1 use crate::ast::{AngleBracketedArgs, ParenthesizedArgs, AttrStyle, BareFnTy};
2 use crate::ast::{GenericBound, TraitBoundModifier};
3 use crate::ast::Unsafety;
4 use crate::ast::{Mod, AnonConst, Arg, Arm, Guard, Attribute, BindingMode, TraitItemKind};
6 use crate::ast::{BlockCheckMode, CaptureBy, Movability};
7 use crate::ast::{Constness, Crate};
8 use crate::ast::Defaultness;
9 use crate::ast::EnumDef;
10 use crate::ast::{Expr, ExprKind, RangeLimits};
11 use crate::ast::{Field, FnDecl, FnHeader};
12 use crate::ast::{ForeignItem, ForeignItemKind, FunctionRetTy};
13 use crate::ast::{GenericParam, GenericParamKind};
14 use crate::ast::GenericArg;
15 use crate::ast::{Ident, ImplItem, IsAsync, IsAuto, Item, ItemKind};
16 use crate::ast::{Label, Lifetime, Lit, LitKind};
17 use crate::ast::Local;
18 use crate::ast::MacStmtStyle;
19 use crate::ast::{Mac, Mac_, MacDelimiter};
20 use crate::ast::{MutTy, Mutability};
21 use crate::ast::{Pat, PatKind, PathSegment};
22 use crate::ast::{PolyTraitRef, QSelf};
23 use crate::ast::{Stmt, StmtKind};
24 use crate::ast::{VariantData, StructField};
25 use crate::ast::StrStyle;
26 use crate::ast::SelfKind;
27 use crate::ast::{TraitItem, TraitRef, TraitObjectSyntax};
28 use crate::ast::{Ty, TyKind, TypeBinding, GenericBounds};
29 use crate::ast::{Visibility, VisibilityKind, WhereClause, CrateSugar};
30 use crate::ast::{UseTree, UseTreeKind};
31 use crate::ast::{BinOpKind, UnOp};
32 use crate::ast::{RangeEnd, RangeSyntax};
33 use crate::{ast, attr};
34 use crate::ext::base::DummyResult;
35 use crate::source_map::{self, SourceMap, Spanned, respan};
36 use crate::parse::{self, SeqSep, classify, token};
37 use crate::parse::lexer::{TokenAndSpan, UnmatchedBrace};
38 use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
39 use crate::parse::token::DelimToken;
40 use crate::parse::{new_sub_parser_from_file, ParseSess, Directory, DirectoryOwnership};
41 use crate::util::parser::{AssocOp, Fixity};
42 use crate::print::pprust;
44 use crate::parse::PResult;
46 use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
47 use crate::symbol::{Symbol, keywords};
49 use errors::{Applicability, DiagnosticBuilder, DiagnosticId, FatalError};
50 use rustc_target::spec::abi::{self, Abi};
51 use syntax_pos::{Span, MultiSpan, BytePos, FileName};
52 use log::{debug, trace};
57 use std::path::{self, Path, PathBuf};
61 /// Whether the type alias or associated type is a concrete type or an existential type
63 /// Just a new name for the same type
65 /// Only trait impls of the type will be usable, not the actual type itself
66 Existential(GenericBounds),
70 struct Restrictions: u8 {
71 const STMT_EXPR = 1 << 0;
72 const NO_STRUCT_LITERAL = 1 << 1;
76 type ItemInfo = (Ident, ItemKind, Option<Vec<Attribute>>);
78 /// Specifies how to parse a path.
79 #[derive(Copy, Clone, PartialEq)]
81 /// In some contexts, notably in expressions, paths with generic arguments are ambiguous
82 /// with something else. For example, in expressions `segment < ....` can be interpreted
83 /// as a comparison and `segment ( ....` can be interpreted as a function call.
84 /// In all such contexts the non-path interpretation is preferred by default for practical
85 /// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g.
86 /// `x<y>` - comparisons, `x::<y>` - unambiguously a path.
88 /// In other contexts, notably in types, no ambiguity exists and paths can be written
89 /// without the disambiguator, e.g., `x<y>` - unambiguously a path.
90 /// Paths with disambiguators are still accepted, `x::<Y>` - unambiguously a path too.
92 /// A path with generic arguments disallowed, e.g., `foo::bar::Baz`, used in imports,
93 /// visibilities or attributes.
94 /// Technically, this variant is unnecessary and e.g., `Expr` can be used instead
95 /// (paths in "mod" contexts have to be checked later for absence of generic arguments
96 /// anyway, due to macros), but it is used to avoid weird suggestions about expected
97 /// tokens when something goes wrong.
101 #[derive(Clone, Copy, PartialEq, Debug)]
108 #[derive(Clone, Copy, PartialEq, Debug)]
114 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
115 /// dropped into the token stream, which happens while parsing the result of
116 /// macro expansion). Placement of these is not as complex as I feared it would
117 /// be. The important thing is to make sure that lookahead doesn't balk at
118 /// `token::Interpolated` tokens.
119 macro_rules! maybe_whole_expr {
121 if let token::Interpolated(nt) = &$p.token {
123 token::NtExpr(e) | token::NtLiteral(e) => {
128 token::NtPath(path) => {
129 let path = path.clone();
131 return Ok($p.mk_expr($p.span, ExprKind::Path(None, path), ThinVec::new()));
133 token::NtBlock(block) => {
134 let block = block.clone();
136 return Ok($p.mk_expr($p.span, ExprKind::Block(block, None), ThinVec::new()));
144 /// As maybe_whole_expr, but for things other than expressions
145 macro_rules! maybe_whole {
146 ($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
147 if let token::Interpolated(nt) = &$p.token {
148 if let token::$constructor(x) = &**nt {
157 /// If the next tokens are ill-formed `$ty::` recover them as `<$ty>::`.
158 macro_rules! maybe_recover_from_interpolated_ty_qpath {
159 ($self: expr, $allow_qpath_recovery: expr) => {
160 if $allow_qpath_recovery && $self.look_ahead(1, |t| t == &token::ModSep) {
161 if let token::Interpolated(nt) = &$self.token {
162 if let token::NtTy(ty) = &**nt {
165 return $self.maybe_recover_from_bad_qpath_stage_2($self.prev_span, ty);
172 fn maybe_append(mut lhs: Vec<Attribute>, mut rhs: Option<Vec<Attribute>>) -> Vec<Attribute> {
173 if let Some(ref mut rhs) = rhs {
179 #[derive(Debug, Clone, Copy, PartialEq)]
190 trait RecoverQPath: Sized + 'static {
191 const PATH_STYLE: PathStyle = PathStyle::Expr;
192 fn to_ty(&self) -> Option<P<Ty>>;
193 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self;
196 impl RecoverQPath for Ty {
197 const PATH_STYLE: PathStyle = PathStyle::Type;
198 fn to_ty(&self) -> Option<P<Ty>> {
199 Some(P(self.clone()))
201 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
202 Self { span: path.span, node: TyKind::Path(qself, path), id: ast::DUMMY_NODE_ID }
206 impl RecoverQPath for Pat {
207 fn to_ty(&self) -> Option<P<Ty>> {
210 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
211 Self { span: path.span, node: PatKind::Path(qself, path), id: ast::DUMMY_NODE_ID }
215 impl RecoverQPath for Expr {
216 fn to_ty(&self) -> Option<P<Ty>> {
219 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
220 Self { span: path.span, node: ExprKind::Path(qself, path),
221 attrs: ThinVec::new(), id: ast::DUMMY_NODE_ID }
225 /* ident is handled by common.rs */
228 pub struct Parser<'a> {
229 pub sess: &'a ParseSess,
230 /// the current token:
231 pub token: token::Token,
232 /// the span of the current token:
234 /// the span of the previous token:
235 meta_var_span: Option<Span>,
237 /// the previous token kind
238 prev_token_kind: PrevTokenKind,
239 restrictions: Restrictions,
240 /// Used to determine the path to externally loaded source files
241 crate directory: Directory<'a>,
242 /// Whether to parse sub-modules in other files.
243 pub recurse_into_file_modules: bool,
244 /// Name of the root module this parser originated from. If `None`, then the
245 /// name is not known. This does not change while the parser is descending
246 /// into modules, and sub-parsers have new values for this name.
247 pub root_module_name: Option<String>,
248 crate expected_tokens: Vec<TokenType>,
249 token_cursor: TokenCursor,
250 desugar_doc_comments: bool,
251 /// Whether we should configure out of line modules as we parse.
253 /// This field is used to keep track of how many left angle brackets we have seen. This is
254 /// required in order to detect extra leading left angle brackets (`<` characters) and error
257 /// See the comments in the `parse_path_segment` function for more details.
258 crate unmatched_angle_bracket_count: u32,
259 crate max_angle_bracket_count: u32,
260 /// List of all unclosed delimiters found by the lexer. If an entry is used for error recovery
261 /// it gets removed from here. Every entry left at the end gets emitted as an independent
263 crate unclosed_delims: Vec<UnmatchedBrace>,
264 last_unexpected_token_span: Option<Span>,
267 impl<'a> Drop for Parser<'a> {
269 let diag = self.diagnostic();
270 emit_unclosed_delims(&mut self.unclosed_delims, diag);
276 frame: TokenCursorFrame,
277 stack: Vec<TokenCursorFrame>,
281 struct TokenCursorFrame {
282 delim: token::DelimToken,
285 tree_cursor: tokenstream::Cursor,
287 last_token: LastToken,
290 /// This is used in `TokenCursorFrame` above to track tokens that are consumed
291 /// by the parser, and then that's transitively used to record the tokens that
292 /// each parse AST item is created with.
294 /// Right now this has two states, either collecting tokens or not collecting
295 /// tokens. If we're collecting tokens we just save everything off into a local
296 /// `Vec`. This should eventually though likely save tokens from the original
297 /// token stream and just use slicing of token streams to avoid creation of a
298 /// whole new vector.
300 /// The second state is where we're passively not recording tokens, but the last
301 /// token is still tracked for when we want to start recording tokens. This
302 /// "last token" means that when we start recording tokens we'll want to ensure
303 /// that this, the first token, is included in the output.
305 /// You can find some more example usage of this in the `collect_tokens` method
309 Collecting(Vec<TreeAndJoint>),
310 Was(Option<TreeAndJoint>),
313 impl TokenCursorFrame {
314 fn new(sp: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self {
318 open_delim: delim == token::NoDelim,
319 tree_cursor: tts.clone().into_trees(),
320 close_delim: delim == token::NoDelim,
321 last_token: LastToken::Was(None),
327 fn next(&mut self) -> TokenAndSpan {
329 let tree = if !self.frame.open_delim {
330 self.frame.open_delim = true;
331 TokenTree::open_tt(self.frame.span.open, self.frame.delim)
332 } else if let Some(tree) = self.frame.tree_cursor.next() {
334 } else if !self.frame.close_delim {
335 self.frame.close_delim = true;
336 TokenTree::close_tt(self.frame.span.close, self.frame.delim)
337 } else if let Some(frame) = self.stack.pop() {
341 return TokenAndSpan { tok: token::Eof, sp: syntax_pos::DUMMY_SP }
344 match self.frame.last_token {
345 LastToken::Collecting(ref mut v) => v.push(tree.clone().into()),
346 LastToken::Was(ref mut t) => *t = Some(tree.clone().into()),
350 TokenTree::Token(sp, tok) => return TokenAndSpan { tok: tok, sp: sp },
351 TokenTree::Delimited(sp, delim, tts) => {
352 let frame = TokenCursorFrame::new(sp, delim, &tts);
353 self.stack.push(mem::replace(&mut self.frame, frame));
359 fn next_desugared(&mut self) -> TokenAndSpan {
360 let (sp, name) = match self.next() {
361 TokenAndSpan { sp, tok: token::DocComment(name) } => (sp, name),
365 let stripped = strip_doc_comment_decoration(&name.as_str());
367 // Searches for the occurrences of `"#*` and returns the minimum number of `#`s
368 // required to wrap the text.
369 let mut num_of_hashes = 0;
371 for ch in stripped.chars() {
374 '#' if count > 0 => count + 1,
377 num_of_hashes = cmp::max(num_of_hashes, count);
380 let delim_span = DelimSpan::from_single(sp);
381 let body = TokenTree::Delimited(
384 [TokenTree::Token(sp, token::Ident(ast::Ident::from_str("doc"), false)),
385 TokenTree::Token(sp, token::Eq),
386 TokenTree::Token(sp, token::Literal(
387 token::StrRaw(Symbol::intern(&stripped), num_of_hashes), None))
389 .iter().cloned().collect::<TokenStream>().into(),
392 self.stack.push(mem::replace(&mut self.frame, TokenCursorFrame::new(
395 &if doc_comment_style(&name.as_str()) == AttrStyle::Inner {
396 [TokenTree::Token(sp, token::Pound), TokenTree::Token(sp, token::Not), body]
397 .iter().cloned().collect::<TokenStream>().into()
399 [TokenTree::Token(sp, token::Pound), body]
400 .iter().cloned().collect::<TokenStream>().into()
408 #[derive(Clone, PartialEq)]
409 crate enum TokenType {
411 Keyword(keywords::Keyword),
421 fn to_string(&self) -> String {
423 TokenType::Token(ref t) => format!("`{}`", pprust::token_to_string(t)),
424 TokenType::Keyword(kw) => format!("`{}`", kw.name()),
425 TokenType::Operator => "an operator".to_string(),
426 TokenType::Lifetime => "lifetime".to_string(),
427 TokenType::Ident => "identifier".to_string(),
428 TokenType::Path => "path".to_string(),
429 TokenType::Type => "type".to_string(),
430 TokenType::Const => "const".to_string(),
435 /// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`,
436 /// `IDENT<<u8 as Trait>::AssocTy>`.
438 /// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
439 /// that `IDENT` is not the ident of a fn trait.
440 fn can_continue_type_after_non_fn_ident(t: &token::Token) -> bool {
441 t == &token::ModSep || t == &token::Lt ||
442 t == &token::BinOp(token::Shl)
445 /// Information about the path to a module.
446 pub struct ModulePath {
449 pub result: Result<ModulePathSuccess, Error>,
452 pub struct ModulePathSuccess {
454 pub directory_ownership: DirectoryOwnership,
459 FileNotFoundForModule {
461 default_path: String,
462 secondary_path: String,
467 default_path: String,
468 secondary_path: String,
471 InclusiveRangeWithNoEnd,
475 fn span_err<S: Into<MultiSpan>>(self,
477 handler: &errors::Handler) -> DiagnosticBuilder<'_> {
479 Error::FileNotFoundForModule { ref mod_name,
483 let mut err = struct_span_err!(handler, sp, E0583,
484 "file not found for module `{}`", mod_name);
485 err.help(&format!("name the file either {} or {} inside the directory \"{}\"",
491 Error::DuplicatePaths { ref mod_name, ref default_path, ref secondary_path } => {
492 let mut err = struct_span_err!(handler, sp, E0584,
493 "file for module `{}` found at both {} and {}",
497 err.help("delete or rename one of them to remove the ambiguity");
500 Error::UselessDocComment => {
501 let mut err = struct_span_err!(handler, sp, E0585,
502 "found a documentation comment that doesn't document anything");
503 err.help("doc comments must come before what they document, maybe a comment was \
504 intended with `//`?");
507 Error::InclusiveRangeWithNoEnd => {
508 let mut err = struct_span_err!(handler, sp, E0586,
509 "inclusive range with no end");
510 err.help("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)");
520 AttributesParsed(ThinVec<Attribute>),
521 AlreadyParsed(P<Expr>),
524 impl From<Option<ThinVec<Attribute>>> for LhsExpr {
525 fn from(o: Option<ThinVec<Attribute>>) -> Self {
526 if let Some(attrs) = o {
527 LhsExpr::AttributesParsed(attrs)
529 LhsExpr::NotYetParsed
534 impl From<P<Expr>> for LhsExpr {
535 fn from(expr: P<Expr>) -> Self {
536 LhsExpr::AlreadyParsed(expr)
540 /// Creates a placeholder argument.
541 fn dummy_arg(span: Span) -> Arg {
542 let ident = Ident::new(keywords::Invalid.name(), span);
544 id: ast::DUMMY_NODE_ID,
545 node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None),
551 id: ast::DUMMY_NODE_ID
553 Arg { ty: P(ty), pat: pat, id: ast::DUMMY_NODE_ID }
556 #[derive(Copy, Clone, Debug)]
557 enum TokenExpectType {
562 impl<'a> Parser<'a> {
563 pub fn new(sess: &'a ParseSess,
565 directory: Option<Directory<'a>>,
566 recurse_into_file_modules: bool,
567 desugar_doc_comments: bool)
569 let mut parser = Parser {
571 token: token::Whitespace,
572 span: syntax_pos::DUMMY_SP,
573 prev_span: syntax_pos::DUMMY_SP,
575 prev_token_kind: PrevTokenKind::Other,
576 restrictions: Restrictions::empty(),
577 recurse_into_file_modules,
578 directory: Directory {
579 path: Cow::from(PathBuf::new()),
580 ownership: DirectoryOwnership::Owned { relative: None }
582 root_module_name: None,
583 expected_tokens: Vec::new(),
584 token_cursor: TokenCursor {
585 frame: TokenCursorFrame::new(
592 desugar_doc_comments,
594 unmatched_angle_bracket_count: 0,
595 max_angle_bracket_count: 0,
596 unclosed_delims: Vec::new(),
597 last_unexpected_token_span: None,
600 let tok = parser.next_tok();
601 parser.token = tok.tok;
602 parser.span = tok.sp;
604 if let Some(directory) = directory {
605 parser.directory = directory;
606 } else if !parser.span.is_dummy() {
607 if let FileName::Real(mut path) = sess.source_map().span_to_unmapped_path(parser.span) {
609 parser.directory.path = Cow::from(path);
613 parser.process_potential_macro_variable();
617 fn next_tok(&mut self) -> TokenAndSpan {
618 let mut next = if self.desugar_doc_comments {
619 self.token_cursor.next_desugared()
621 self.token_cursor.next()
623 if next.sp.is_dummy() {
624 // Tweak the location for better diagnostics, but keep syntactic context intact.
625 next.sp = self.prev_span.with_ctxt(next.sp.ctxt());
630 /// Converts the current token to a string using `self`'s reader.
631 pub fn this_token_to_string(&self) -> String {
632 pprust::token_to_string(&self.token)
635 fn token_descr(&self) -> Option<&'static str> {
636 Some(match &self.token {
637 t if t.is_special_ident() => "reserved identifier",
638 t if t.is_used_keyword() => "keyword",
639 t if t.is_unused_keyword() => "reserved keyword",
640 token::DocComment(..) => "doc comment",
645 fn this_token_descr(&self) -> String {
646 if let Some(prefix) = self.token_descr() {
647 format!("{} `{}`", prefix, self.this_token_to_string())
649 format!("`{}`", self.this_token_to_string())
653 fn unexpected_last<T>(&self, t: &token::Token) -> PResult<'a, T> {
654 let token_str = pprust::token_to_string(t);
655 Err(self.span_fatal(self.prev_span, &format!("unexpected token: `{}`", token_str)))
658 crate fn unexpected<T>(&mut self) -> PResult<'a, T> {
659 match self.expect_one_of(&[], &[]) {
661 Ok(_) => unreachable!(),
665 /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
666 pub fn expect(&mut self, t: &token::Token) -> PResult<'a, bool /* recovered */> {
667 if self.expected_tokens.is_empty() {
668 if self.token == *t {
672 let token_str = pprust::token_to_string(t);
673 let this_token_str = self.this_token_descr();
674 let mut err = self.fatal(&format!("expected `{}`, found {}",
678 let sp = if self.token == token::Token::Eof {
679 // EOF, don't want to point at the following char, but rather the last token
682 self.sess.source_map().next_point(self.prev_span)
684 let label_exp = format!("expected `{}`", token_str);
685 match self.recover_closing_delimiter(&[t.clone()], err) {
688 return Ok(recovered);
691 let cm = self.sess.source_map();
692 match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
693 (Ok(ref a), Ok(ref b)) if a.line == b.line => {
694 // When the spans are in the same line, it means that the only content
695 // between them is whitespace, point only at the found token.
696 err.span_label(self.span, label_exp);
699 err.span_label(sp, label_exp);
700 err.span_label(self.span, "unexpected token");
706 self.expect_one_of(slice::from_ref(t), &[])
710 fn recover_closing_delimiter(
712 tokens: &[token::Token],
713 mut err: DiagnosticBuilder<'a>,
714 ) -> PResult<'a, bool> {
716 // we want to use the last closing delim that would apply
717 for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
718 if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
719 && Some(self.span) > unmatched.unclosed_span
726 // Recover and assume that the detected unclosed delimiter was meant for
727 // this location. Emit the diagnostic and act as if the delimiter was
728 // present for the parser's sake.
730 // Don't attempt to recover from this unclosed delimiter more than once.
731 let unmatched = self.unclosed_delims.remove(pos);
732 let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
734 // We want to suggest the inclusion of the closing delimiter where it makes
735 // the most sense, which is immediately after the last token:
740 // | help: `)` may belong here (FIXME: #58270)
742 // unclosed delimiter
743 if let Some(sp) = unmatched.unclosed_span {
744 err.span_label(sp, "unclosed delimiter");
746 err.span_suggestion_short(
747 self.sess.source_map().next_point(self.prev_span),
748 &format!("{} may belong here", delim.to_string()),
750 Applicability::MaybeIncorrect,
753 self.expected_tokens.clear(); // reduce errors
760 /// Expect next token to be edible or inedible token. If edible,
761 /// then consume it; if inedible, then return without consuming
762 /// anything. Signal a fatal error if next token is unexpected.
763 pub fn expect_one_of(
765 edible: &[token::Token],
766 inedible: &[token::Token],
767 ) -> PResult<'a, bool /* recovered */> {
768 fn tokens_to_string(tokens: &[TokenType]) -> String {
769 let mut i = tokens.iter();
770 // This might be a sign we need a connect method on Iterator.
772 .map_or(String::new(), |t| t.to_string());
773 i.enumerate().fold(b, |mut b, (i, a)| {
774 if tokens.len() > 2 && i == tokens.len() - 2 {
776 } else if tokens.len() == 2 && i == tokens.len() - 2 {
781 b.push_str(&a.to_string());
785 if edible.contains(&self.token) {
788 } else if inedible.contains(&self.token) {
789 // leave it in the input
791 } else if self.last_unexpected_token_span == Some(self.span) {
794 let mut expected = edible.iter()
795 .map(|x| TokenType::Token(x.clone()))
796 .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
797 .chain(self.expected_tokens.iter().cloned())
798 .collect::<Vec<_>>();
799 expected.sort_by_cached_key(|x| x.to_string());
801 let expect = tokens_to_string(&expected[..]);
802 let actual = self.this_token_to_string();
803 let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
804 let short_expect = if expected.len() > 6 {
805 format!("{} possible tokens", expected.len())
809 (format!("expected one of {}, found `{}`", expect, actual),
810 (self.sess.source_map().next_point(self.prev_span),
811 format!("expected one of {} here", short_expect)))
812 } else if expected.is_empty() {
813 (format!("unexpected token: `{}`", actual),
814 (self.prev_span, "unexpected token after this".to_string()))
816 (format!("expected {}, found `{}`", expect, actual),
817 (self.sess.source_map().next_point(self.prev_span),
818 format!("expected {} here", expect)))
820 self.last_unexpected_token_span = Some(self.span);
821 let mut err = self.fatal(&msg_exp);
822 if self.token.is_ident_named("and") {
823 err.span_suggestion_short(
825 "use `&&` instead of `and` for the boolean operator",
827 Applicability::MaybeIncorrect,
830 if self.token.is_ident_named("or") {
831 err.span_suggestion_short(
833 "use `||` instead of `or` for the boolean operator",
835 Applicability::MaybeIncorrect,
838 let sp = if self.token == token::Token::Eof {
839 // This is EOF, don't want to point at the following char, but rather the last token
844 match self.recover_closing_delimiter(&expected.iter().filter_map(|tt| match tt {
845 TokenType::Token(t) => Some(t.clone()),
847 }).collect::<Vec<_>>(), err) {
850 return Ok(recovered);
854 let cm = self.sess.source_map();
855 match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
856 (Ok(ref a), Ok(ref b)) if a.line == b.line => {
857 // When the spans are in the same line, it means that the only content between
858 // them is whitespace, point at the found token in that case:
860 // X | () => { syntax error };
861 // | ^^^^^ expected one of 8 possible tokens here
863 // instead of having:
865 // X | () => { syntax error };
866 // | -^^^^^ unexpected token
868 // | expected one of 8 possible tokens here
869 err.span_label(self.span, label_exp);
871 _ if self.prev_span == syntax_pos::DUMMY_SP => {
872 // Account for macro context where the previous span might not be
873 // available to avoid incorrect output (#54841).
874 err.span_label(self.span, "unexpected token");
877 err.span_label(sp, label_exp);
878 err.span_label(self.span, "unexpected token");
885 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
886 fn interpolated_or_expr_span(&self,
887 expr: PResult<'a, P<Expr>>)
888 -> PResult<'a, (Span, P<Expr>)> {
890 if self.prev_token_kind == PrevTokenKind::Interpolated {
898 fn expected_ident_found(&self) -> DiagnosticBuilder<'a> {
899 let mut err = self.struct_span_err(self.span,
900 &format!("expected identifier, found {}",
901 self.this_token_descr()));
902 if let token::Ident(ident, false) = &self.token {
903 if ident.is_raw_guess() {
906 "you can escape reserved keywords to use them as identifiers",
907 format!("r#{}", ident),
908 Applicability::MaybeIncorrect,
912 if let Some(token_descr) = self.token_descr() {
913 err.span_label(self.span, format!("expected identifier, found {}", token_descr));
915 err.span_label(self.span, "expected identifier");
916 if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
921 Applicability::MachineApplicable,
928 pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
929 self.parse_ident_common(true)
932 fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> {
934 token::Ident(ident, _) => {
935 if self.token.is_reserved_ident() {
936 let mut err = self.expected_ident_found();
943 let span = self.span;
945 Ok(Ident::new(ident.name, span))
948 Err(if self.prev_token_kind == PrevTokenKind::DocComment {
949 self.span_fatal_err(self.prev_span, Error::UselessDocComment)
951 self.expected_ident_found()
957 /// Checks if the next token is `tok`, and returns `true` if so.
959 /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
961 crate fn check(&mut self, tok: &token::Token) -> bool {
962 let is_present = self.token == *tok;
963 if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
967 /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
968 pub fn eat(&mut self, tok: &token::Token) -> bool {
969 let is_present = self.check(tok);
970 if is_present { self.bump() }
974 fn check_keyword(&mut self, kw: keywords::Keyword) -> bool {
975 self.expected_tokens.push(TokenType::Keyword(kw));
976 self.token.is_keyword(kw)
979 /// If the next token is the given keyword, eats it and returns
980 /// `true`. Otherwise, returns `false`.
981 pub fn eat_keyword(&mut self, kw: keywords::Keyword) -> bool {
982 if self.check_keyword(kw) {
990 fn eat_keyword_noexpect(&mut self, kw: keywords::Keyword) -> bool {
991 if self.token.is_keyword(kw) {
999 /// If the given word is not a keyword, signals an error.
1000 /// If the next token is not the given word, signals an error.
1001 /// Otherwise, eats it.
1002 fn expect_keyword(&mut self, kw: keywords::Keyword) -> PResult<'a, ()> {
1003 if !self.eat_keyword(kw) {
1010 fn check_ident(&mut self) -> bool {
1011 if self.token.is_ident() {
1014 self.expected_tokens.push(TokenType::Ident);
1019 fn check_path(&mut self) -> bool {
1020 if self.token.is_path_start() {
1023 self.expected_tokens.push(TokenType::Path);
1028 fn check_type(&mut self) -> bool {
1029 if self.token.can_begin_type() {
1032 self.expected_tokens.push(TokenType::Type);
1037 fn check_const_arg(&mut self) -> bool {
1038 if self.token.can_begin_const_arg() {
1041 self.expected_tokens.push(TokenType::Const);
1046 /// Expects and consumes a `+`. if `+=` is seen, replaces it with a `=`
1047 /// and continues. If a `+` is not seen, returns `false`.
1049 /// This is used when token-splitting `+=` into `+`.
1050 /// See issue #47856 for an example of when this may occur.
1051 fn eat_plus(&mut self) -> bool {
1052 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
1054 token::BinOp(token::Plus) => {
1058 token::BinOpEq(token::Plus) => {
1059 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1060 self.bump_with(token::Eq, span);
1068 /// Checks to see if the next token is either `+` or `+=`.
1069 /// Otherwise returns `false`.
1070 fn check_plus(&mut self) -> bool {
1071 if self.token.is_like_plus() {
1075 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
1080 /// Expects and consumes an `&`. If `&&` is seen, replaces it with a single
1081 /// `&` and continues. If an `&` is not seen, signals an error.
1082 fn expect_and(&mut self) -> PResult<'a, ()> {
1083 self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
1085 token::BinOp(token::And) => {
1090 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1091 Ok(self.bump_with(token::BinOp(token::And), span))
1093 _ => self.unexpected()
1097 /// Expects and consumes an `|`. If `||` is seen, replaces it with a single
1098 /// `|` and continues. If an `|` is not seen, signals an error.
1099 fn expect_or(&mut self) -> PResult<'a, ()> {
1100 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or)));
1102 token::BinOp(token::Or) => {
1107 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1108 Ok(self.bump_with(token::BinOp(token::Or), span))
1110 _ => self.unexpected()
1114 fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
1116 None => {/* everything ok */}
1118 let text = suf.as_str();
1119 if text.is_empty() {
1120 self.span_bug(sp, "found empty literal suffix in Some")
1122 self.struct_span_err(sp, &format!("suffixes on {} are invalid", kind))
1123 .span_label(sp, format!("invalid suffix `{}`", text))
1129 /// Attempts to consume a `<`. If `<<` is seen, replaces it with a single
1130 /// `<` and continue. If `<-` is seen, replaces it with a single `<`
1131 /// and continue. If a `<` is not seen, returns false.
1133 /// This is meant to be used when parsing generics on a path to get the
1135 fn eat_lt(&mut self) -> bool {
1136 self.expected_tokens.push(TokenType::Token(token::Lt));
1137 let ate = match self.token {
1142 token::BinOp(token::Shl) => {
1143 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1144 self.bump_with(token::Lt, span);
1148 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1149 self.bump_with(token::BinOp(token::Minus), span);
1156 // See doc comment for `unmatched_angle_bracket_count`.
1157 self.unmatched_angle_bracket_count += 1;
1158 self.max_angle_bracket_count += 1;
1159 debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count);
1165 fn expect_lt(&mut self) -> PResult<'a, ()> {
1173 /// Expects and consumes a single `>` token. if a `>>` is seen, replaces it
1174 /// with a single `>` and continues. If a `>` is not seen, signals an error.
1175 fn expect_gt(&mut self) -> PResult<'a, ()> {
1176 self.expected_tokens.push(TokenType::Token(token::Gt));
1177 let ate = match self.token {
1182 token::BinOp(token::Shr) => {
1183 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1184 Some(self.bump_with(token::Gt, span))
1186 token::BinOpEq(token::Shr) => {
1187 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1188 Some(self.bump_with(token::Ge, span))
1191 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1192 Some(self.bump_with(token::Eq, span))
1199 // See doc comment for `unmatched_angle_bracket_count`.
1200 if self.unmatched_angle_bracket_count > 0 {
1201 self.unmatched_angle_bracket_count -= 1;
1202 debug!("expect_gt: (decrement) count={:?}", self.unmatched_angle_bracket_count);
1207 None => self.unexpected(),
1211 /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
1212 /// passes through any errors encountered. Used for error recovery.
1213 fn eat_to_tokens(&mut self, kets: &[&token::Token]) {
1214 let handler = self.diagnostic();
1216 if let Err(ref mut err) = self.parse_seq_to_before_tokens(kets,
1218 TokenExpectType::Expect,
1219 |p| Ok(p.parse_token_tree())) {
1220 handler.cancel(err);
1224 /// Parses a sequence, including the closing delimiter. The function
1225 /// `f` must consume tokens until reaching the next separator or
1226 /// closing bracket.
1227 pub fn parse_seq_to_end<T, F>(&mut self,
1231 -> PResult<'a, Vec<T>> where
1232 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
1234 let (val, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
1241 /// Parses a sequence, not including the closing delimiter. The function
1242 /// `f` must consume tokens until reaching the next separator or
1243 /// closing bracket.
1244 pub fn parse_seq_to_before_end<T, F>(
1249 ) -> PResult<'a, (Vec<T>, bool)>
1250 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
1252 self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
1255 fn parse_seq_to_before_tokens<T, F>(
1257 kets: &[&token::Token],
1259 expect: TokenExpectType,
1261 ) -> PResult<'a, (Vec<T>, bool /* recovered */)>
1262 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
1264 let mut first = true;
1265 let mut recovered = false;
1267 while !kets.iter().any(|k| {
1269 TokenExpectType::Expect => self.check(k),
1270 TokenExpectType::NoExpect => self.token == **k,
1274 token::CloseDelim(..) | token::Eof => break,
1277 if let Some(ref t) = sep.sep {
1281 match self.expect(t) {
1288 // Attempt to keep parsing if it was a similar separator
1289 if let Some(ref tokens) = t.similar_tokens() {
1290 if tokens.contains(&self.token) {
1295 // Attempt to keep parsing if it was an omitted separator
1310 if sep.trailing_sep_allowed && kets.iter().any(|k| {
1312 TokenExpectType::Expect => self.check(k),
1313 TokenExpectType::NoExpect => self.token == **k,
1326 /// Parses a sequence, including the closing delimiter. The function
1327 /// `f` must consume tokens until reaching the next separator or
1328 /// closing bracket.
1329 fn parse_unspanned_seq<T, F>(
1335 ) -> PResult<'a, Vec<T>> where
1336 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
1339 let (result, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
1346 /// Advance the parser by one token
1347 pub fn bump(&mut self) {
1348 if self.prev_token_kind == PrevTokenKind::Eof {
1349 // Bumping after EOF is a bad sign, usually an infinite loop.
1350 self.bug("attempted to bump the parser past EOF (may be stuck in a loop)");
1353 self.prev_span = self.meta_var_span.take().unwrap_or(self.span);
1355 // Record last token kind for possible error recovery.
1356 self.prev_token_kind = match self.token {
1357 token::DocComment(..) => PrevTokenKind::DocComment,
1358 token::Comma => PrevTokenKind::Comma,
1359 token::BinOp(token::Plus) => PrevTokenKind::Plus,
1360 token::Interpolated(..) => PrevTokenKind::Interpolated,
1361 token::Eof => PrevTokenKind::Eof,
1362 token::Ident(..) => PrevTokenKind::Ident,
1363 _ => PrevTokenKind::Other,
1366 let next = self.next_tok();
1367 self.span = next.sp;
1368 self.token = next.tok;
1369 self.expected_tokens.clear();
1370 // check after each token
1371 self.process_potential_macro_variable();
1374 /// Advance the parser using provided token as a next one. Use this when
1375 /// consuming a part of a token. For example a single `<` from `<<`.
1376 fn bump_with(&mut self, next: token::Token, span: Span) {
1377 self.prev_span = self.span.with_hi(span.lo());
1378 // It would be incorrect to record the kind of the current token, but
1379 // fortunately for tokens currently using `bump_with`, the
1380 // prev_token_kind will be of no use anyway.
1381 self.prev_token_kind = PrevTokenKind::Other;
1384 self.expected_tokens.clear();
1387 pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where
1388 F: FnOnce(&token::Token) -> R,
1391 return f(&self.token)
1394 f(&match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1395 Some(tree) => match tree {
1396 TokenTree::Token(_, tok) => tok,
1397 TokenTree::Delimited(_, delim, _) => token::OpenDelim(delim),
1399 None => token::CloseDelim(self.token_cursor.frame.delim),
1403 fn look_ahead_span(&self, dist: usize) -> Span {
1408 match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1409 Some(TokenTree::Token(span, _)) => span,
1410 Some(TokenTree::Delimited(span, ..)) => span.entire(),
1411 None => self.look_ahead_span(dist - 1),
1414 pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
1415 self.sess.span_diagnostic.struct_span_fatal(self.span, m)
1417 pub fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
1418 self.sess.span_diagnostic.struct_span_fatal(sp, m)
1420 fn span_fatal_err<S: Into<MultiSpan>>(&self, sp: S, err: Error) -> DiagnosticBuilder<'a> {
1421 err.span_err(sp, self.diagnostic())
1423 fn bug(&self, m: &str) -> ! {
1424 self.sess.span_diagnostic.span_bug(self.span, m)
1426 fn span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) {
1427 self.sess.span_diagnostic.span_err(sp, m)
1429 fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
1430 self.sess.span_diagnostic.struct_span_err(sp, m)
1432 crate fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
1433 self.sess.span_diagnostic.span_bug(sp, m)
1436 fn cancel(&self, err: &mut DiagnosticBuilder<'_>) {
1437 self.sess.span_diagnostic.cancel(err)
1440 crate fn diagnostic(&self) -> &'a errors::Handler {
1441 &self.sess.span_diagnostic
1444 /// Is the current token one of the keywords that signals a bare function type?
1445 fn token_is_bare_fn_keyword(&mut self) -> bool {
1446 self.check_keyword(keywords::Fn) ||
1447 self.check_keyword(keywords::Unsafe) ||
1448 self.check_keyword(keywords::Extern)
1451 /// Parses a `TyKind::BareFn` type.
1452 fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
1455 [unsafe] [extern "ABI"] fn (S) -> T
1465 let unsafety = self.parse_unsafety();
1466 let abi = if self.eat_keyword(keywords::Extern) {
1467 self.parse_opt_abi()?.unwrap_or(Abi::C)
1472 self.expect_keyword(keywords::Fn)?;
1473 let (inputs, c_variadic) = self.parse_fn_args(false, true)?;
1474 let ret_ty = self.parse_ret_ty(false)?;
1475 let decl = P(FnDecl {
1480 Ok(TyKind::BareFn(P(BareFnTy {
1488 /// Parses asyncness: `async` or nothing.
1489 fn parse_asyncness(&mut self) -> IsAsync {
1490 if self.eat_keyword(keywords::Async) {
1492 closure_id: ast::DUMMY_NODE_ID,
1493 return_impl_trait_id: ast::DUMMY_NODE_ID,
1500 /// Parses unsafety: `unsafe` or nothing.
1501 fn parse_unsafety(&mut self) -> Unsafety {
1502 if self.eat_keyword(keywords::Unsafe) {
1509 /// Parses the items in a trait declaration.
1510 pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
1511 maybe_whole!(self, NtTraitItem, |x| x);
1512 let attrs = self.parse_outer_attributes()?;
1513 let mut unclosed_delims = vec![];
1514 let (mut item, tokens) = self.collect_tokens(|this| {
1515 let item = this.parse_trait_item_(at_end, attrs);
1516 unclosed_delims.append(&mut this.unclosed_delims);
1519 self.unclosed_delims.append(&mut unclosed_delims);
1520 // See `parse_item` for why this clause is here.
1521 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
1522 item.tokens = Some(tokens);
1527 fn parse_trait_item_(&mut self,
1529 mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
1532 let (name, node, generics) = if self.eat_keyword(keywords::Type) {
1533 self.parse_trait_item_assoc_ty()?
1534 } else if self.is_const_item() {
1535 self.expect_keyword(keywords::Const)?;
1536 let ident = self.parse_ident()?;
1537 self.expect(&token::Colon)?;
1538 let ty = self.parse_ty()?;
1539 let default = if self.eat(&token::Eq) {
1540 let expr = self.parse_expr()?;
1541 self.expect(&token::Semi)?;
1544 self.expect(&token::Semi)?;
1547 (ident, TraitItemKind::Const(ty, default), ast::Generics::default())
1548 } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
1549 // trait item macro.
1550 (keywords::Invalid.ident(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
1552 let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
1554 let ident = self.parse_ident()?;
1555 let mut generics = self.parse_generics()?;
1557 let d = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| {
1558 // This is somewhat dubious; We don't want to allow
1559 // argument names to be left off if there is a
1562 // We don't allow argument names to be left off in edition 2018.
1563 p.parse_arg_general(p.span.rust_2018(), true, false)
1565 generics.where_clause = self.parse_where_clause()?;
1567 let sig = ast::MethodSig {
1577 let body = match self.token {
1581 debug!("parse_trait_methods(): parsing required method");
1584 token::OpenDelim(token::Brace) => {
1585 debug!("parse_trait_methods(): parsing provided method");
1587 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1588 attrs.extend(inner_attrs.iter().cloned());
1591 token::Interpolated(ref nt) => {
1593 token::NtBlock(..) => {
1595 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1596 attrs.extend(inner_attrs.iter().cloned());
1600 let token_str = self.this_token_descr();
1601 let mut err = self.fatal(&format!("expected `;` or `{{`, found {}",
1603 err.span_label(self.span, "expected `;` or `{`");
1609 let token_str = self.this_token_descr();
1610 let mut err = self.fatal(&format!("expected `;` or `{{`, found {}",
1612 err.span_label(self.span, "expected `;` or `{`");
1616 (ident, ast::TraitItemKind::Method(sig, body), generics)
1620 id: ast::DUMMY_NODE_ID,
1625 span: lo.to(self.prev_span),
1630 /// Parses an optional return type `[ -> TY ]` in a function declaration.
1631 fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
1632 if self.eat(&token::RArrow) {
1633 Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?))
1635 Ok(FunctionRetTy::Default(self.span.shrink_to_lo()))
1640 pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
1641 self.parse_ty_common(true, true, false)
1644 /// Parses a type in restricted contexts where `+` is not permitted.
1646 /// Example 1: `&'a TYPE`
1647 /// `+` is prohibited to maintain operator priority (P(+) < P(&)).
1648 /// Example 2: `value1 as TYPE + value2`
1649 /// `+` is prohibited to avoid interactions with expression grammar.
1650 fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
1651 self.parse_ty_common(false, true, false)
1654 fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
1655 allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
1656 maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
1657 maybe_whole!(self, NtTy, |x| x);
1660 let mut impl_dyn_multi = false;
1661 let node = if self.eat(&token::OpenDelim(token::Paren)) {
1662 // `(TYPE)` is a parenthesized type.
1663 // `(TYPE,)` is a tuple with a single field of type TYPE.
1664 let mut ts = vec![];
1665 let mut last_comma = false;
1666 while self.token != token::CloseDelim(token::Paren) {
1667 ts.push(self.parse_ty()?);
1668 if self.eat(&token::Comma) {
1675 let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
1676 self.expect(&token::CloseDelim(token::Paren))?;
1678 if ts.len() == 1 && !last_comma {
1679 let ty = ts.into_iter().nth(0).unwrap().into_inner();
1680 let maybe_bounds = allow_plus && self.token.is_like_plus();
1682 // `(TY_BOUND_NOPAREN) + BOUND + ...`.
1683 TyKind::Path(None, ref path) if maybe_bounds => {
1684 self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
1686 TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
1687 if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
1688 let path = match bounds[0] {
1689 GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
1690 GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
1692 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1695 _ => TyKind::Paren(P(ty))
1700 } else if self.eat(&token::Not) {
1703 } else if self.eat(&token::BinOp(token::Star)) {
1705 TyKind::Ptr(self.parse_ptr()?)
1706 } else if self.eat(&token::OpenDelim(token::Bracket)) {
1708 let t = self.parse_ty()?;
1709 // Parse optional `; EXPR` in `[TYPE; EXPR]`
1710 let t = match self.maybe_parse_fixed_length_of_vec()? {
1711 None => TyKind::Slice(t),
1712 Some(length) => TyKind::Array(t, AnonConst {
1713 id: ast::DUMMY_NODE_ID,
1717 self.expect(&token::CloseDelim(token::Bracket))?;
1719 } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
1722 self.parse_borrowed_pointee()?
1723 } else if self.eat_keyword_noexpect(keywords::Typeof) {
1725 // In order to not be ambiguous, the type must be surrounded by parens.
1726 self.expect(&token::OpenDelim(token::Paren))?;
1728 id: ast::DUMMY_NODE_ID,
1729 value: self.parse_expr()?,
1731 self.expect(&token::CloseDelim(token::Paren))?;
1733 } else if self.eat_keyword(keywords::Underscore) {
1734 // A type to be inferred `_`
1736 } else if self.token_is_bare_fn_keyword() {
1737 // Function pointer type
1738 self.parse_ty_bare_fn(Vec::new())?
1739 } else if self.check_keyword(keywords::For) {
1740 // Function pointer type or bound list (trait object type) starting with a poly-trait.
1741 // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
1742 // `for<'lt> Trait1<'lt> + Trait2 + 'a`
1744 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
1745 if self.token_is_bare_fn_keyword() {
1746 self.parse_ty_bare_fn(lifetime_defs)?
1748 let path = self.parse_path(PathStyle::Type)?;
1749 let parse_plus = allow_plus && self.check_plus();
1750 self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
1752 } else if self.eat_keyword(keywords::Impl) {
1753 // Always parse bounds greedily for better error recovery.
1754 let bounds = self.parse_generic_bounds(None)?;
1755 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1756 TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
1757 } else if self.check_keyword(keywords::Dyn) &&
1758 (self.span.rust_2018() ||
1759 self.look_ahead(1, |t| t.can_begin_bound() &&
1760 !can_continue_type_after_non_fn_ident(t))) {
1761 self.bump(); // `dyn`
1762 // Always parse bounds greedily for better error recovery.
1763 let bounds = self.parse_generic_bounds(None)?;
1764 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1765 TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
1766 } else if self.check(&token::Question) ||
1767 self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
1768 // Bound list (trait object type)
1769 TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?,
1770 TraitObjectSyntax::None)
1771 } else if self.eat_lt() {
1773 let (qself, path) = self.parse_qpath(PathStyle::Type)?;
1774 TyKind::Path(Some(qself), path)
1775 } else if self.token.is_path_start() {
1777 let path = self.parse_path(PathStyle::Type)?;
1778 if self.eat(&token::Not) {
1779 // Macro invocation in type position
1780 let (delim, tts) = self.expect_delimited_token_tree()?;
1781 let node = Mac_ { path, tts, delim };
1782 TyKind::Mac(respan(lo.to(self.prev_span), node))
1784 // Just a type path or bound list (trait object type) starting with a trait.
1786 // `Trait1 + Trait2 + 'a`
1787 if allow_plus && self.check_plus() {
1788 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1790 TyKind::Path(None, path)
1793 } else if self.check(&token::DotDotDot) {
1794 if allow_c_variadic {
1795 self.eat(&token::DotDotDot);
1798 return Err(self.fatal(
1799 "only foreign functions are allowed to be C-variadic"
1803 let msg = format!("expected type, found {}", self.this_token_descr());
1804 return Err(self.fatal(&msg));
1807 let span = lo.to(self.prev_span);
1808 let ty = P(Ty { node, span, id: ast::DUMMY_NODE_ID });
1810 // Try to recover from use of `+` with incorrect priority.
1811 self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
1812 self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
1813 self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
1816 fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
1817 lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
1818 let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
1819 let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
1821 self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
1822 bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
1824 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
1827 fn maybe_report_ambiguous_plus(&mut self, allow_plus: bool, impl_dyn_multi: bool, ty: &Ty) {
1828 if !allow_plus && impl_dyn_multi {
1829 let sum_with_parens = format!("({})", pprust::ty_to_string(&ty));
1830 self.struct_span_err(ty.span, "ambiguous `+` in a type")
1833 "use parentheses to disambiguate",
1835 Applicability::MachineApplicable
1840 fn maybe_recover_from_bad_type_plus(&mut self, allow_plus: bool, ty: &Ty) -> PResult<'a, ()> {
1841 // Do not add `+` to expected tokens.
1842 if !allow_plus || !self.token.is_like_plus() {
1847 let bounds = self.parse_generic_bounds(None)?;
1848 let sum_span = ty.span.to(self.prev_span);
1850 let mut err = struct_span_err!(self.sess.span_diagnostic, sum_span, E0178,
1851 "expected a path on the left-hand side of `+`, not `{}`", pprust::ty_to_string(ty));
1854 TyKind::Rptr(ref lifetime, ref mut_ty) => {
1855 let sum_with_parens = pprust::to_string(|s| {
1856 use crate::print::pprust::PrintState;
1859 s.print_opt_lifetime(lifetime)?;
1860 s.print_mutability(mut_ty.mutbl)?;
1862 s.print_type(&mut_ty.ty)?;
1863 s.print_type_bounds(" +", &bounds)?;
1866 err.span_suggestion(
1868 "try adding parentheses",
1870 Applicability::MachineApplicable
1873 TyKind::Ptr(..) | TyKind::BareFn(..) => {
1874 err.span_label(sum_span, "perhaps you forgot parentheses?");
1877 err.span_label(sum_span, "expected a path");
1884 /// Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`.
1885 /// Attempt to convert the base expression/pattern/type into a type, parse the `::AssocItem`
1886 /// tail, and combine them into a `<Ty>::AssocItem` expression/pattern/type.
1887 fn maybe_recover_from_bad_qpath<T: RecoverQPath>(&mut self, base: P<T>, allow_recovery: bool)
1888 -> PResult<'a, P<T>> {
1889 // Do not add `::` to expected tokens.
1890 if allow_recovery && self.token == token::ModSep {
1891 if let Some(ty) = base.to_ty() {
1892 return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
1898 /// Given an already parsed `Ty` parse the `::AssocItem` tail and
1899 /// combine them into a `<Ty>::AssocItem` expression/pattern/type.
1900 fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(&mut self, ty_span: Span, ty: P<Ty>)
1901 -> PResult<'a, P<T>> {
1902 self.expect(&token::ModSep)?;
1904 let mut path = ast::Path { segments: Vec::new(), span: syntax_pos::DUMMY_SP };
1905 self.parse_path_segments(&mut path.segments, T::PATH_STYLE)?;
1906 path.span = ty_span.to(self.prev_span);
1908 let ty_str = self.sess.source_map().span_to_snippet(ty_span)
1909 .unwrap_or_else(|_| pprust::ty_to_string(&ty));
1911 .struct_span_err(path.span, "missing angle brackets in associated item path")
1912 .span_suggestion( // this is a best-effort recovery
1913 path.span, "try", format!("<{}>::{}", ty_str, path), Applicability::MaybeIncorrect
1916 let path_span = ty_span.shrink_to_hi(); // use an empty path since `position` == 0
1917 Ok(P(T::recovered(Some(QSelf { ty, path_span, position: 0 }), path)))
1920 fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
1921 let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
1922 let mutbl = self.parse_mutability();
1923 let ty = self.parse_ty_no_plus()?;
1924 return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
1927 fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
1928 let mutbl = if self.eat_keyword(keywords::Mut) {
1930 } else if self.eat_keyword(keywords::Const) {
1931 Mutability::Immutable
1933 let span = self.prev_span;
1934 let msg = "expected mut or const in raw pointer type";
1935 self.struct_span_err(span, msg)
1936 .span_label(span, msg)
1937 .help("use `*mut T` or `*const T` as appropriate")
1939 Mutability::Immutable
1941 let t = self.parse_ty_no_plus()?;
1942 Ok(MutTy { ty: t, mutbl: mutbl })
1945 fn is_named_argument(&mut self) -> bool {
1946 let offset = match self.token {
1947 token::Interpolated(ref nt) => match **nt {
1948 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
1951 token::BinOp(token::And) | token::AndAnd => 1,
1952 _ if self.token.is_keyword(keywords::Mut) => 1,
1956 self.look_ahead(offset, |t| t.is_ident()) &&
1957 self.look_ahead(offset + 1, |t| t == &token::Colon)
1960 /// Skips unexpected attributes and doc comments in this position and emits an appropriate
1962 fn eat_incorrect_doc_comment(&mut self, applied_to: &str) {
1963 if let token::DocComment(_) = self.token {
1964 let mut err = self.diagnostic().struct_span_err(
1966 &format!("documentation comments cannot be applied to {}", applied_to),
1968 err.span_label(self.span, "doc comments are not allowed here");
1971 } else if self.token == token::Pound && self.look_ahead(1, |t| {
1972 *t == token::OpenDelim(token::Bracket)
1975 // Skip every token until next possible arg.
1976 while self.token != token::CloseDelim(token::Bracket) {
1979 let sp = lo.to(self.span);
1981 let mut err = self.diagnostic().struct_span_err(
1983 &format!("attributes cannot be applied to {}", applied_to),
1985 err.span_label(sp, "attributes are not allowed here");
1990 /// This version of parse arg doesn't necessarily require identifier names.
1991 fn parse_arg_general(&mut self, require_name: bool, is_trait_item: bool,
1992 allow_c_variadic: bool) -> PResult<'a, Arg> {
1993 maybe_whole!(self, NtArg, |x| x);
1995 if let Ok(Some(_)) = self.parse_self_arg() {
1996 let mut err = self.struct_span_err(self.prev_span,
1997 "unexpected `self` argument in function");
1998 err.span_label(self.prev_span,
1999 "`self` is only valid as the first argument of an associated function");
2003 let (pat, ty) = if require_name || self.is_named_argument() {
2004 debug!("parse_arg_general parse_pat (require_name:{})",
2006 self.eat_incorrect_doc_comment("method arguments");
2007 let pat = self.parse_pat(Some("argument name"))?;
2009 if let Err(mut err) = self.expect(&token::Colon) {
2010 // If we find a pattern followed by an identifier, it could be an (incorrect)
2011 // C-style parameter declaration.
2012 if self.check_ident() && self.look_ahead(1, |t| {
2013 *t == token::Comma || *t == token::CloseDelim(token::Paren)
2015 let ident = self.parse_ident().unwrap();
2016 let span = pat.span.with_hi(ident.span.hi());
2018 err.span_suggestion(
2020 "declare the type after the parameter binding",
2021 String::from("<identifier>: <type>"),
2022 Applicability::HasPlaceholders,
2024 } else if require_name && is_trait_item {
2025 if let PatKind::Ident(_, ident, _) = pat.node {
2026 err.span_suggestion(
2028 "explicitly ignore parameter",
2029 format!("_: {}", ident),
2030 Applicability::MachineApplicable,
2034 err.note("anonymous parameters are removed in the 2018 edition (see RFC 1685)");
2040 self.eat_incorrect_doc_comment("a method argument's type");
2041 (pat, self.parse_ty_common(true, true, allow_c_variadic)?)
2043 debug!("parse_arg_general ident_to_pat");
2044 let parser_snapshot_before_ty = self.clone();
2045 self.eat_incorrect_doc_comment("a method argument's type");
2046 let mut ty = self.parse_ty_common(true, true, allow_c_variadic);
2047 if ty.is_ok() && self.token != token::Comma &&
2048 self.token != token::CloseDelim(token::Paren) {
2049 // This wasn't actually a type, but a pattern looking like a type,
2050 // so we are going to rollback and re-parse for recovery.
2051 ty = self.unexpected();
2055 let ident = Ident::new(keywords::Invalid.name(), self.prev_span);
2057 id: ast::DUMMY_NODE_ID,
2058 node: PatKind::Ident(
2059 BindingMode::ByValue(Mutability::Immutable), ident, None),
2065 // If this is a C-variadic argument and we hit an error, return the
2067 if self.token == token::DotDotDot {
2070 // Recover from attempting to parse the argument as a type without pattern.
2072 mem::replace(self, parser_snapshot_before_ty);
2073 let pat = self.parse_pat(Some("argument name"))?;
2074 self.expect(&token::Colon)?;
2075 let ty = self.parse_ty()?;
2077 let mut err = self.diagnostic().struct_span_err_with_code(
2079 "patterns aren't allowed in methods without bodies",
2080 DiagnosticId::Error("E0642".into()),
2082 err.span_suggestion_short(
2084 "give this argument a name or use an underscore to ignore it",
2086 Applicability::MachineApplicable,
2090 // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
2092 node: PatKind::Wild,
2094 id: ast::DUMMY_NODE_ID
2101 Ok(Arg { ty, pat, id: ast::DUMMY_NODE_ID })
2104 /// Parses a single function argument.
2105 crate fn parse_arg(&mut self) -> PResult<'a, Arg> {
2106 self.parse_arg_general(true, false, false)
2109 /// Parses an argument in a lambda header (e.g., `|arg, arg|`).
2110 fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
2111 let pat = self.parse_pat(Some("argument name"))?;
2112 let t = if self.eat(&token::Colon) {
2116 id: ast::DUMMY_NODE_ID,
2117 node: TyKind::Infer,
2118 span: self.prev_span,
2124 id: ast::DUMMY_NODE_ID
2128 fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
2129 if self.eat(&token::Semi) {
2130 Ok(Some(self.parse_expr()?))
2136 /// Matches `token_lit = LIT_INTEGER | ...`.
2137 fn parse_lit_token(&mut self) -> PResult<'a, LitKind> {
2138 let out = match self.token {
2139 token::Interpolated(ref nt) => match **nt {
2140 token::NtExpr(ref v) | token::NtLiteral(ref v) => match v.node {
2141 ExprKind::Lit(ref lit) => { lit.node.clone() }
2142 _ => { return self.unexpected_last(&self.token); }
2144 _ => { return self.unexpected_last(&self.token); }
2146 token::Literal(lit, suf) => {
2147 let diag = Some((self.span, &self.sess.span_diagnostic));
2148 let (suffix_illegal, result) = parse::lit_token(lit, suf, diag);
2152 self.expect_no_suffix(sp, &format!("a {}", lit.literal_name()), suf)
2157 token::Dot if self.look_ahead(1, |t| match t {
2158 token::Literal(parse::token::Lit::Integer(_) , _) => true,
2160 }) => { // recover from `let x = .4;`
2163 if let token::Literal(
2164 parse::token::Lit::Integer(val),
2167 let suffix = suffix.and_then(|s| {
2168 let s = s.as_str().get();
2169 if ["f32", "f64"].contains(&s) {
2176 let sp = lo.to(self.prev_span);
2177 let mut err = self.diagnostic()
2178 .struct_span_err(sp, "float literals must have an integer part");
2179 err.span_suggestion(
2181 "must have an integer part",
2182 format!("0.{}{}", val, suffix),
2183 Applicability::MachineApplicable,
2186 return Ok(match suffix {
2187 "f32" => ast::LitKind::Float(val, ast::FloatTy::F32),
2188 "f64" => ast::LitKind::Float(val, ast::FloatTy::F64),
2189 _ => ast::LitKind::FloatUnsuffixed(val),
2195 _ => { return self.unexpected_last(&self.token); }
2202 /// Matches `lit = true | false | token_lit`.
2203 crate fn parse_lit(&mut self) -> PResult<'a, Lit> {
2205 let lit = if self.eat_keyword(keywords::True) {
2207 } else if self.eat_keyword(keywords::False) {
2208 LitKind::Bool(false)
2210 let lit = self.parse_lit_token()?;
2213 Ok(source_map::Spanned { node: lit, span: lo.to(self.prev_span) })
2216 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
2217 crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
2218 maybe_whole_expr!(self);
2220 let minus_lo = self.span;
2221 let minus_present = self.eat(&token::BinOp(token::Minus));
2223 let literal = self.parse_lit()?;
2224 let hi = self.prev_span;
2225 let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
2228 let minus_hi = self.prev_span;
2229 let unary = self.mk_unary(UnOp::Neg, expr);
2230 Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
2236 fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> {
2238 token::Ident(ident, _) if self.token.is_path_segment_keyword() => {
2239 let span = self.span;
2241 Ok(Ident::new(ident.name, span))
2243 _ => self.parse_ident(),
2247 fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
2249 token::Ident(ident, false) if ident.name == keywords::Underscore.name() => {
2250 let span = self.span;
2252 Ok(Ident::new(ident.name, span))
2254 _ => self.parse_ident(),
2258 /// Parses a qualified path.
2259 /// Assumes that the leading `<` has been parsed already.
2261 /// `qualified_path = <type [as trait_ref]>::path`
2266 /// `<T as U>::F::a<S>` (without disambiguator)
2267 /// `<T as U>::F::a::<S>` (with disambiguator)
2268 fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> {
2269 let lo = self.prev_span;
2270 let ty = self.parse_ty()?;
2272 // `path` will contain the prefix of the path up to the `>`,
2273 // if any (e.g., `U` in the `<T as U>::*` examples
2274 // above). `path_span` has the span of that path, or an empty
2275 // span in the case of something like `<T>::Bar`.
2276 let (mut path, path_span);
2277 if self.eat_keyword(keywords::As) {
2278 let path_lo = self.span;
2279 path = self.parse_path(PathStyle::Type)?;
2280 path_span = path_lo.to(self.prev_span);
2282 path = ast::Path { segments: Vec::new(), span: syntax_pos::DUMMY_SP };
2283 path_span = self.span.to(self.span);
2286 // See doc comment for `unmatched_angle_bracket_count`.
2287 self.expect(&token::Gt)?;
2288 if self.unmatched_angle_bracket_count > 0 {
2289 self.unmatched_angle_bracket_count -= 1;
2290 debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
2293 self.expect(&token::ModSep)?;
2295 let qself = QSelf { ty, path_span, position: path.segments.len() };
2296 self.parse_path_segments(&mut path.segments, style)?;
2298 Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) }))
2301 /// Parses simple paths.
2303 /// `path = [::] segment+`
2304 /// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
2307 /// `a::b::C<D>` (without disambiguator)
2308 /// `a::b::C::<D>` (with disambiguator)
2309 /// `Fn(Args)` (without disambiguator)
2310 /// `Fn::(Args)` (with disambiguator)
2311 pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
2312 maybe_whole!(self, NtPath, |path| {
2313 if style == PathStyle::Mod &&
2314 path.segments.iter().any(|segment| segment.args.is_some()) {
2315 self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
2320 let lo = self.meta_var_span.unwrap_or(self.span);
2321 let mut segments = Vec::new();
2322 let mod_sep_ctxt = self.span.ctxt();
2323 if self.eat(&token::ModSep) {
2324 segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
2326 self.parse_path_segments(&mut segments, style)?;
2328 Ok(ast::Path { segments, span: lo.to(self.prev_span) })
2331 /// Like `parse_path`, but also supports parsing `Word` meta items into paths for
2332 /// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]`
2334 pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
2335 let meta_ident = match self.token {
2336 token::Interpolated(ref nt) => match **nt {
2337 token::NtMeta(ref meta) => match meta.node {
2338 ast::MetaItemKind::Word => Some(meta.path.clone()),
2345 if let Some(path) = meta_ident {
2349 self.parse_path(style)
2352 fn parse_path_segments(&mut self,
2353 segments: &mut Vec<PathSegment>,
2355 -> PResult<'a, ()> {
2357 let segment = self.parse_path_segment(style)?;
2358 if style == PathStyle::Expr {
2359 // In order to check for trailing angle brackets, we must have finished
2360 // recursing (`parse_path_segment` can indirectly call this function),
2361 // that is, the next token must be the highlighted part of the below example:
2363 // `Foo::<Bar as Baz<T>>::Qux`
2366 // As opposed to the below highlight (if we had only finished the first
2369 // `Foo::<Bar as Baz<T>>::Qux`
2372 // `PathStyle::Expr` is only provided at the root invocation and never in
2373 // `parse_path_segment` to recurse and therefore can be checked to maintain
2375 self.check_trailing_angle_brackets(&segment, token::ModSep);
2377 segments.push(segment);
2379 if self.is_import_coupler() || !self.eat(&token::ModSep) {
2385 fn parse_path_segment(&mut self, style: PathStyle) -> PResult<'a, PathSegment> {
2386 let ident = self.parse_path_segment_ident()?;
2388 let is_args_start = |token: &token::Token| match *token {
2389 token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren) => true,
2392 let check_args_start = |this: &mut Self| {
2393 this.expected_tokens.extend_from_slice(
2394 &[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
2396 is_args_start(&this.token)
2399 Ok(if style == PathStyle::Type && check_args_start(self) ||
2400 style != PathStyle::Mod && self.check(&token::ModSep)
2401 && self.look_ahead(1, |t| is_args_start(t)) {
2402 // We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
2403 // it isn't, then we reset the unmatched angle bracket count as we're about to start
2404 // parsing a new path.
2405 if style == PathStyle::Expr {
2406 self.unmatched_angle_bracket_count = 0;
2407 self.max_angle_bracket_count = 0;
2410 // Generic arguments are found - `<`, `(`, `::<` or `::(`.
2411 self.eat(&token::ModSep);
2413 let args = if self.eat_lt() {
2415 let (args, bindings) =
2416 self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?;
2418 let span = lo.to(self.prev_span);
2419 AngleBracketedArgs { args, bindings, span }.into()
2423 let (inputs, recovered) = self.parse_seq_to_before_tokens(
2424 &[&token::CloseDelim(token::Paren)],
2425 SeqSep::trailing_allowed(token::Comma),
2426 TokenExpectType::Expect,
2431 let span = lo.to(self.prev_span);
2432 let output = if self.eat(&token::RArrow) {
2433 Some(self.parse_ty_common(false, false, false)?)
2437 ParenthesizedArgs { inputs, output, span }.into()
2440 PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
2442 // Generic arguments are not found.
2443 PathSegment::from_ident(ident)
2447 crate fn check_lifetime(&mut self) -> bool {
2448 self.expected_tokens.push(TokenType::Lifetime);
2449 self.token.is_lifetime()
2452 /// Parses a single lifetime `'a` or panics.
2453 crate fn expect_lifetime(&mut self) -> Lifetime {
2454 if let Some(ident) = self.token.lifetime() {
2455 let span = self.span;
2457 Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
2459 self.span_bug(self.span, "not a lifetime")
2463 fn eat_label(&mut self) -> Option<Label> {
2464 if let Some(ident) = self.token.lifetime() {
2465 let span = self.span;
2467 Some(Label { ident: Ident::new(ident.name, span) })
2473 /// Parses mutability (`mut` or nothing).
2474 fn parse_mutability(&mut self) -> Mutability {
2475 if self.eat_keyword(keywords::Mut) {
2478 Mutability::Immutable
2482 fn parse_field_name(&mut self) -> PResult<'a, Ident> {
2483 if let token::Literal(token::Integer(name), suffix) = self.token {
2484 self.expect_no_suffix(self.span, "a tuple index", suffix);
2486 Ok(Ident::new(name, self.prev_span))
2488 self.parse_ident_common(false)
2492 /// Parse ident (COLON expr)?
2493 fn parse_field(&mut self) -> PResult<'a, Field> {
2494 let attrs = self.parse_outer_attributes()?;
2497 // Check if a colon exists one ahead. This means we're parsing a fieldname.
2498 let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| {
2499 t == &token::Colon || t == &token::Eq
2501 let fieldname = self.parse_field_name()?;
2503 // Check for an equals token. This means the source incorrectly attempts to
2504 // initialize a field with an eq rather than a colon.
2505 if self.token == token::Eq {
2507 .struct_span_err(self.span, "expected `:`, found `=`")
2509 fieldname.span.shrink_to_hi().to(self.span),
2510 "replace equals symbol with a colon",
2512 Applicability::MachineApplicable,
2517 (fieldname, self.parse_expr()?, false)
2519 let fieldname = self.parse_ident_common(false)?;
2521 // Mimic `x: x` for the `x` field shorthand.
2522 let path = ast::Path::from_ident(fieldname);
2523 let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new());
2524 (fieldname, expr, true)
2528 span: lo.to(expr.span),
2531 attrs: attrs.into(),
2535 fn mk_expr(&mut self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
2536 P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
2539 fn mk_unary(&mut self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
2540 ExprKind::Unary(unop, expr)
2543 fn mk_binary(&mut self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
2544 ExprKind::Binary(binop, lhs, rhs)
2547 fn mk_call(&mut self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
2548 ExprKind::Call(f, args)
2551 fn mk_index(&mut self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
2552 ExprKind::Index(expr, idx)
2555 fn mk_range(&mut self,
2556 start: Option<P<Expr>>,
2557 end: Option<P<Expr>>,
2558 limits: RangeLimits)
2559 -> PResult<'a, ast::ExprKind> {
2560 if end.is_none() && limits == RangeLimits::Closed {
2561 Err(self.span_fatal_err(self.span, Error::InclusiveRangeWithNoEnd))
2563 Ok(ExprKind::Range(start, end, limits))
2567 fn mk_assign_op(&mut self, binop: ast::BinOp,
2568 lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
2569 ExprKind::AssignOp(binop, lhs, rhs)
2572 fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
2573 let delim = match self.token {
2574 token::OpenDelim(delim) => delim,
2576 let msg = "expected open delimiter";
2577 let mut err = self.fatal(msg);
2578 err.span_label(self.span, msg);
2582 let tts = match self.parse_token_tree() {
2583 TokenTree::Delimited(_, _, tts) => tts,
2584 _ => unreachable!(),
2586 let delim = match delim {
2587 token::Paren => MacDelimiter::Parenthesis,
2588 token::Bracket => MacDelimiter::Bracket,
2589 token::Brace => MacDelimiter::Brace,
2590 token::NoDelim => self.bug("unexpected no delimiter"),
2592 Ok((delim, tts.into()))
2595 /// At the bottom (top?) of the precedence hierarchy,
2596 /// Parses things like parenthesized exprs, macros, `return`, etc.
2598 /// N.B., this does not parse outer attributes, and is private because it only works
2599 /// correctly if called from `parse_dot_or_call_expr()`.
2600 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
2601 maybe_recover_from_interpolated_ty_qpath!(self, true);
2602 maybe_whole_expr!(self);
2604 // Outer attributes are already parsed and will be
2605 // added to the return value after the fact.
2607 // Therefore, prevent sub-parser from parsing
2608 // attributes by giving them a empty "already parsed" list.
2609 let mut attrs = ThinVec::new();
2612 let mut hi = self.span;
2616 // Note: when adding new syntax here, don't forget to adjust Token::can_begin_expr().
2618 token::OpenDelim(token::Paren) => {
2621 attrs.extend(self.parse_inner_attributes()?);
2623 // (e) is parenthesized e
2624 // (e,) is a tuple with only one field, e
2625 let mut es = vec![];
2626 let mut trailing_comma = false;
2627 let mut recovered = false;
2628 while self.token != token::CloseDelim(token::Paren) {
2629 es.push(self.parse_expr()?);
2630 recovered = self.expect_one_of(
2632 &[token::Comma, token::CloseDelim(token::Paren)],
2634 if self.eat(&token::Comma) {
2635 trailing_comma = true;
2637 trailing_comma = false;
2645 hi = self.prev_span;
2646 ex = if es.len() == 1 && !trailing_comma {
2647 ExprKind::Paren(es.into_iter().nth(0).unwrap())
2652 token::OpenDelim(token::Brace) => {
2653 return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
2655 token::BinOp(token::Or) | token::OrOr => {
2656 return self.parse_lambda_expr(attrs);
2658 token::OpenDelim(token::Bracket) => {
2661 attrs.extend(self.parse_inner_attributes()?);
2663 if self.eat(&token::CloseDelim(token::Bracket)) {
2665 ex = ExprKind::Array(Vec::new());
2668 let first_expr = self.parse_expr()?;
2669 if self.eat(&token::Semi) {
2670 // Repeating array syntax: [ 0; 512 ]
2671 let count = AnonConst {
2672 id: ast::DUMMY_NODE_ID,
2673 value: self.parse_expr()?,
2675 self.expect(&token::CloseDelim(token::Bracket))?;
2676 ex = ExprKind::Repeat(first_expr, count);
2677 } else if self.eat(&token::Comma) {
2678 // Vector with two or more elements.
2679 let remaining_exprs = self.parse_seq_to_end(
2680 &token::CloseDelim(token::Bracket),
2681 SeqSep::trailing_allowed(token::Comma),
2682 |p| Ok(p.parse_expr()?)
2684 let mut exprs = vec![first_expr];
2685 exprs.extend(remaining_exprs);
2686 ex = ExprKind::Array(exprs);
2688 // Vector with one element.
2689 self.expect(&token::CloseDelim(token::Bracket))?;
2690 ex = ExprKind::Array(vec![first_expr]);
2693 hi = self.prev_span;
2697 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
2699 return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
2701 if self.span.rust_2018() && self.check_keyword(keywords::Async)
2703 if self.is_async_block() { // check for `async {` and `async move {`
2704 return self.parse_async_block(attrs);
2706 return self.parse_lambda_expr(attrs);
2709 if self.check_keyword(keywords::Move) || self.check_keyword(keywords::Static) {
2710 return self.parse_lambda_expr(attrs);
2712 if self.eat_keyword(keywords::If) {
2713 return self.parse_if_expr(attrs);
2715 if self.eat_keyword(keywords::For) {
2716 let lo = self.prev_span;
2717 return self.parse_for_expr(None, lo, attrs);
2719 if self.eat_keyword(keywords::While) {
2720 let lo = self.prev_span;
2721 return self.parse_while_expr(None, lo, attrs);
2723 if let Some(label) = self.eat_label() {
2724 let lo = label.ident.span;
2725 self.expect(&token::Colon)?;
2726 if self.eat_keyword(keywords::While) {
2727 return self.parse_while_expr(Some(label), lo, attrs)
2729 if self.eat_keyword(keywords::For) {
2730 return self.parse_for_expr(Some(label), lo, attrs)
2732 if self.eat_keyword(keywords::Loop) {
2733 return self.parse_loop_expr(Some(label), lo, attrs)
2735 if self.token == token::OpenDelim(token::Brace) {
2736 return self.parse_block_expr(Some(label),
2738 BlockCheckMode::Default,
2741 let msg = "expected `while`, `for`, `loop` or `{` after a label";
2742 let mut err = self.fatal(msg);
2743 err.span_label(self.span, msg);
2746 if self.eat_keyword(keywords::Loop) {
2747 let lo = self.prev_span;
2748 return self.parse_loop_expr(None, lo, attrs);
2750 if self.eat_keyword(keywords::Continue) {
2751 let label = self.eat_label();
2752 let ex = ExprKind::Continue(label);
2753 let hi = self.prev_span;
2754 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
2756 if self.eat_keyword(keywords::Match) {
2757 let match_sp = self.prev_span;
2758 return self.parse_match_expr(attrs).map_err(|mut err| {
2759 err.span_label(match_sp, "while parsing this match expression");
2763 if self.eat_keyword(keywords::Unsafe) {
2764 return self.parse_block_expr(
2767 BlockCheckMode::Unsafe(ast::UserProvided),
2770 if self.is_do_catch_block() {
2771 let mut db = self.fatal("found removed `do catch` syntax");
2772 db.help("Following RFC #2388, the new non-placeholder syntax is `try`");
2775 if self.is_try_block() {
2777 assert!(self.eat_keyword(keywords::Try));
2778 return self.parse_try_block(lo, attrs);
2780 if self.eat_keyword(keywords::Return) {
2781 if self.token.can_begin_expr() {
2782 let e = self.parse_expr()?;
2784 ex = ExprKind::Ret(Some(e));
2786 ex = ExprKind::Ret(None);
2788 } else if self.eat_keyword(keywords::Break) {
2789 let label = self.eat_label();
2790 let e = if self.token.can_begin_expr()
2791 && !(self.token == token::OpenDelim(token::Brace)
2792 && self.restrictions.contains(
2793 Restrictions::NO_STRUCT_LITERAL)) {
2794 Some(self.parse_expr()?)
2798 ex = ExprKind::Break(label, e);
2799 hi = self.prev_span;
2800 } else if self.eat_keyword(keywords::Yield) {
2801 if self.token.can_begin_expr() {
2802 let e = self.parse_expr()?;
2804 ex = ExprKind::Yield(Some(e));
2806 ex = ExprKind::Yield(None);
2808 } else if self.token.is_keyword(keywords::Let) {
2809 // Catch this syntax error here, instead of in `parse_ident`, so
2810 // that we can explicitly mention that let is not to be used as an expression
2811 let mut db = self.fatal("expected expression, found statement (`let`)");
2812 db.span_label(self.span, "expected expression");
2813 db.note("variable declaration using `let` is a statement");
2815 } else if self.token.is_path_start() {
2816 let path = self.parse_path(PathStyle::Expr)?;
2818 // `!`, as an operator, is prefix, so we know this isn't that
2819 if self.eat(&token::Not) {
2820 // MACRO INVOCATION expression
2821 let (delim, tts) = self.expect_delimited_token_tree()?;
2822 hi = self.prev_span;
2823 ex = ExprKind::Mac(respan(lo.to(hi), Mac_ { path, tts, delim }));
2824 } else if self.check(&token::OpenDelim(token::Brace)) &&
2825 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL) {
2826 // This is a struct literal, unless we're prohibited
2827 // from parsing struct literals here.
2828 return self.parse_struct_expr(lo, path, attrs);
2831 ex = ExprKind::Path(None, path);
2834 if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
2835 // Don't complain about bare semicolons after unclosed braces
2836 // recovery in order to keep the error count down. Fixing the
2837 // delimiters will possibly also fix the bare semicolon found in
2838 // expression context. For example, silence the following error:
2840 // error: expected expression, found `;`
2844 // | ^ expected expression
2847 return Ok(self.mk_expr(self.span, ExprKind::Err, ThinVec::new()));
2849 match self.parse_literal_maybe_minus() {
2852 ex = expr.node.clone();
2855 self.cancel(&mut err);
2856 let msg = format!("expected expression, found {}",
2857 self.this_token_descr());
2858 let mut err = self.fatal(&msg);
2859 err.span_label(self.span, "expected expression");
2867 let expr = self.mk_expr(lo.to(hi), ex, attrs);
2868 self.maybe_recover_from_bad_qpath(expr, true)
2871 fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>)
2872 -> PResult<'a, P<Expr>> {
2873 let struct_sp = lo.to(self.prev_span);
2875 let mut fields = Vec::new();
2876 let mut base = None;
2878 attrs.extend(self.parse_inner_attributes()?);
2880 while self.token != token::CloseDelim(token::Brace) {
2881 if self.eat(&token::DotDot) {
2882 let exp_span = self.prev_span;
2883 match self.parse_expr() {
2889 self.recover_stmt();
2892 if self.token == token::Comma {
2893 let mut err = self.sess.span_diagnostic.mut_span_err(
2894 exp_span.to(self.prev_span),
2895 "cannot use a comma after the base struct",
2897 err.span_suggestion_short(
2899 "remove this comma",
2901 Applicability::MachineApplicable
2903 err.note("the base struct must always be the last field");
2905 self.recover_stmt();
2910 let mut recovery_field = None;
2911 if let token::Ident(ident, _) = self.token {
2912 if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
2913 // Use in case of error after field-looking code: `S { foo: () with a }`
2914 let mut ident = ident.clone();
2915 ident.span = self.span;
2916 recovery_field = Some(ast::Field {
2919 expr: self.mk_expr(self.span, ExprKind::Err, ThinVec::new()),
2920 is_shorthand: false,
2921 attrs: ThinVec::new(),
2925 let mut parsed_field = None;
2926 match self.parse_field() {
2927 Ok(f) => parsed_field = Some(f),
2929 e.span_label(struct_sp, "while parsing this struct");
2932 // If the next token is a comma, then try to parse
2933 // what comes next as additional fields, rather than
2934 // bailing out until next `}`.
2935 if self.token != token::Comma {
2936 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2937 if self.token != token::Comma {
2944 match self.expect_one_of(&[token::Comma],
2945 &[token::CloseDelim(token::Brace)]) {
2946 Ok(_) => if let Some(f) = parsed_field.or(recovery_field) {
2947 // only include the field if there's no parse error for the field name
2951 if let Some(f) = recovery_field {
2954 e.span_label(struct_sp, "while parsing this struct");
2956 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2957 self.eat(&token::Comma);
2962 let span = lo.to(self.span);
2963 self.expect(&token::CloseDelim(token::Brace))?;
2964 return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
2967 fn parse_or_use_outer_attributes(&mut self,
2968 already_parsed_attrs: Option<ThinVec<Attribute>>)
2969 -> PResult<'a, ThinVec<Attribute>> {
2970 if let Some(attrs) = already_parsed_attrs {
2973 self.parse_outer_attributes().map(|a| a.into())
2977 /// Parses a block or unsafe block.
2978 fn parse_block_expr(&mut self, opt_label: Option<Label>,
2979 lo: Span, blk_mode: BlockCheckMode,
2980 outer_attrs: ThinVec<Attribute>)
2981 -> PResult<'a, P<Expr>> {
2982 self.expect(&token::OpenDelim(token::Brace))?;
2984 let mut attrs = outer_attrs;
2985 attrs.extend(self.parse_inner_attributes()?);
2987 let blk = self.parse_block_tail(lo, blk_mode)?;
2988 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs));
2991 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
2992 fn parse_dot_or_call_expr(&mut self,
2993 already_parsed_attrs: Option<ThinVec<Attribute>>)
2994 -> PResult<'a, P<Expr>> {
2995 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
2997 let b = self.parse_bottom_expr();
2998 let (span, b) = self.interpolated_or_expr_span(b)?;
2999 self.parse_dot_or_call_expr_with(b, span, attrs)
3002 fn parse_dot_or_call_expr_with(&mut self,
3005 mut attrs: ThinVec<Attribute>)
3006 -> PResult<'a, P<Expr>> {
3007 // Stitch the list of outer attributes onto the return value.
3008 // A little bit ugly, but the best way given the current code
3010 self.parse_dot_or_call_expr_with_(e0, lo)
3012 expr.map(|mut expr| {
3013 attrs.extend::<Vec<_>>(expr.attrs.into());
3016 ExprKind::If(..) | ExprKind::IfLet(..) => {
3017 if !expr.attrs.is_empty() {
3018 // Just point to the first attribute in there...
3019 let span = expr.attrs[0].span;
3022 "attributes are not yet allowed on `if` \
3033 // Assuming we have just parsed `.`, continue parsing into an expression.
3034 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
3035 let segment = self.parse_path_segment(PathStyle::Expr)?;
3036 self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
3038 Ok(match self.token {
3039 token::OpenDelim(token::Paren) => {
3040 // Method call `expr.f()`
3041 let mut args = self.parse_unspanned_seq(
3042 &token::OpenDelim(token::Paren),
3043 &token::CloseDelim(token::Paren),
3044 SeqSep::trailing_allowed(token::Comma),
3045 |p| Ok(p.parse_expr()?)
3047 args.insert(0, self_arg);
3049 let span = lo.to(self.prev_span);
3050 self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new())
3053 // Field access `expr.f`
3054 if let Some(args) = segment.args {
3055 self.span_err(args.span(),
3056 "field expressions may not have generic arguments");
3059 let span = lo.to(self.prev_span);
3060 self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::new())
3065 /// This function checks if there are trailing angle brackets and produces
3066 /// a diagnostic to suggest removing them.
3068 /// ```ignore (diagnostic)
3069 /// let _ = vec![1, 2, 3].into_iter().collect::<Vec<usize>>>>();
3070 /// ^^ help: remove extra angle brackets
3072 fn check_trailing_angle_brackets(&mut self, segment: &PathSegment, end: token::Token) {
3073 // This function is intended to be invoked after parsing a path segment where there are two
3076 // 1. A specific token is expected after the path segment.
3077 // eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
3078 // `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
3079 // 2. No specific token is expected after the path segment.
3080 // eg. `x.foo` (field access)
3082 // This function is called after parsing `.foo` and before parsing the token `end` (if
3083 // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
3086 // We only care about trailing angle brackets if we previously parsed angle bracket
3087 // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
3088 // removed in this case:
3090 // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
3092 // This case is particularly tricky as we won't notice it just looking at the tokens -
3093 // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
3094 // have already been parsed):
3096 // `x.foo::<u32>>>(3)`
3097 let parsed_angle_bracket_args = segment.args
3099 .map(|args| args.is_angle_bracketed())
3103 "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
3104 parsed_angle_bracket_args,
3106 if !parsed_angle_bracket_args {
3110 // Keep the span at the start so we can highlight the sequence of `>` characters to be
3114 // We need to look-ahead to see if we have `>` characters without moving the cursor forward
3115 // (since we might have the field access case and the characters we're eating are
3116 // actual operators and not trailing characters - ie `x.foo >> 3`).
3117 let mut position = 0;
3119 // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
3120 // many of each (so we can correctly pluralize our error messages) and continue to
3122 let mut number_of_shr = 0;
3123 let mut number_of_gt = 0;
3124 while self.look_ahead(position, |t| {
3125 trace!("check_trailing_angle_brackets: t={:?}", t);
3126 if *t == token::BinOp(token::BinOpToken::Shr) {
3129 } else if *t == token::Gt {
3139 // If we didn't find any trailing `>` characters, then we have nothing to error about.
3141 "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
3142 number_of_gt, number_of_shr,
3144 if number_of_gt < 1 && number_of_shr < 1 {
3148 // Finally, double check that we have our end token as otherwise this is the
3150 if self.look_ahead(position, |t| {
3151 trace!("check_trailing_angle_brackets: t={:?}", t);
3154 // Eat from where we started until the end token so that parsing can continue
3155 // as if we didn't have those extra angle brackets.
3156 self.eat_to_tokens(&[&end]);
3157 let span = lo.until(self.span);
3159 let plural = number_of_gt > 1 || number_of_shr >= 1;
3163 &format!("unmatched angle bracket{}", if plural { "s" } else { "" }),
3167 &format!("remove extra angle bracket{}", if plural { "s" } else { "" }),
3169 Applicability::MachineApplicable,
3175 fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
3180 while self.eat(&token::Question) {
3181 let hi = self.prev_span;
3182 e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new());
3186 if self.eat(&token::Dot) {
3188 token::Ident(..) => {
3189 e = self.parse_dot_suffix(e, lo)?;
3191 token::Literal(token::Integer(name), suffix) => {
3192 let span = self.span;
3194 let field = ExprKind::Field(e, Ident::new(name, span));
3195 e = self.mk_expr(lo.to(span), field, ThinVec::new());
3197 self.expect_no_suffix(span, "a tuple index", suffix);
3199 token::Literal(token::Float(n), _suf) => {
3201 let fstr = n.as_str();
3202 let mut err = self.diagnostic()
3203 .struct_span_err(self.prev_span, &format!("unexpected token: `{}`", n));
3204 err.span_label(self.prev_span, "unexpected token");
3205 if fstr.chars().all(|x| "0123456789.".contains(x)) {
3206 let float = match fstr.parse::<f64>().ok() {
3210 let sugg = pprust::to_string(|s| {
3211 use crate::print::pprust::PrintState;
3215 s.print_usize(float.trunc() as usize)?;
3218 s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
3220 err.span_suggestion(
3221 lo.to(self.prev_span),
3222 "try parenthesizing the first index",
3224 Applicability::MachineApplicable
3231 // FIXME Could factor this out into non_fatal_unexpected or something.
3232 let actual = self.this_token_to_string();
3233 self.span_err(self.span, &format!("unexpected token: `{}`", actual));
3238 if self.expr_is_complete(&e) { break; }
3241 token::OpenDelim(token::Paren) => {
3242 let es = self.parse_unspanned_seq(
3243 &token::OpenDelim(token::Paren),
3244 &token::CloseDelim(token::Paren),
3245 SeqSep::trailing_allowed(token::Comma),
3246 |p| Ok(p.parse_expr()?)
3248 hi = self.prev_span;
3250 let nd = self.mk_call(e, es);
3251 e = self.mk_expr(lo.to(hi), nd, ThinVec::new());
3255 // Could be either an index expression or a slicing expression.
3256 token::OpenDelim(token::Bracket) => {
3258 let ix = self.parse_expr()?;
3260 self.expect(&token::CloseDelim(token::Bracket))?;
3261 let index = self.mk_index(e, ix);
3262 e = self.mk_expr(lo.to(hi), index, ThinVec::new())
3270 crate fn process_potential_macro_variable(&mut self) {
3271 let (token, span) = match self.token {
3272 token::Dollar if self.span.ctxt() != syntax_pos::hygiene::SyntaxContext::empty() &&
3273 self.look_ahead(1, |t| t.is_ident()) => {
3275 let name = match self.token {
3276 token::Ident(ident, _) => ident,
3279 let mut err = self.fatal(&format!("unknown macro variable `{}`", name));
3280 err.span_label(self.span, "unknown macro variable");
3285 token::Interpolated(ref nt) => {
3286 self.meta_var_span = Some(self.span);
3287 // Interpolated identifier and lifetime tokens are replaced with usual identifier
3288 // and lifetime tokens, so the former are never encountered during normal parsing.
3290 token::NtIdent(ident, is_raw) => (token::Ident(ident, is_raw), ident.span),
3291 token::NtLifetime(ident) => (token::Lifetime(ident), ident.span),
3301 /// Parses a single token tree from the input.
3302 crate fn parse_token_tree(&mut self) -> TokenTree {
3304 token::OpenDelim(..) => {
3305 let frame = mem::replace(&mut self.token_cursor.frame,
3306 self.token_cursor.stack.pop().unwrap());
3307 self.span = frame.span.entire();
3309 TokenTree::Delimited(
3312 frame.tree_cursor.stream.into(),
3315 token::CloseDelim(_) | token::Eof => unreachable!(),
3317 let (token, span) = (mem::replace(&mut self.token, token::Whitespace), self.span);
3319 TokenTree::Token(span, token)
3324 // parse a stream of tokens into a list of TokenTree's,
3326 pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
3327 let mut tts = Vec::new();
3328 while self.token != token::Eof {
3329 tts.push(self.parse_token_tree());
3334 pub fn parse_tokens(&mut self) -> TokenStream {
3335 let mut result = Vec::new();
3338 token::Eof | token::CloseDelim(..) => break,
3339 _ => result.push(self.parse_token_tree().into()),
3342 TokenStream::new(result)
3345 /// Parse a prefix-unary-operator expr
3346 fn parse_prefix_expr(&mut self,
3347 already_parsed_attrs: Option<ThinVec<Attribute>>)
3348 -> PResult<'a, P<Expr>> {
3349 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
3351 // Note: when adding new unary operators, don't forget to adjust Token::can_begin_expr()
3352 let (hi, ex) = match self.token {
3355 let e = self.parse_prefix_expr(None);
3356 let (span, e) = self.interpolated_or_expr_span(e)?;
3357 (lo.to(span), self.mk_unary(UnOp::Not, e))
3359 // Suggest `!` for bitwise negation when encountering a `~`
3362 let e = self.parse_prefix_expr(None);
3363 let (span, e) = self.interpolated_or_expr_span(e)?;
3364 let span_of_tilde = lo;
3365 let mut err = self.diagnostic()
3366 .struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator");
3367 err.span_suggestion_short(
3369 "use `!` to perform bitwise negation",
3371 Applicability::MachineApplicable
3374 (lo.to(span), self.mk_unary(UnOp::Not, e))
3376 token::BinOp(token::Minus) => {
3378 let e = self.parse_prefix_expr(None);
3379 let (span, e) = self.interpolated_or_expr_span(e)?;
3380 (lo.to(span), self.mk_unary(UnOp::Neg, e))
3382 token::BinOp(token::Star) => {
3384 let e = self.parse_prefix_expr(None);
3385 let (span, e) = self.interpolated_or_expr_span(e)?;
3386 (lo.to(span), self.mk_unary(UnOp::Deref, e))
3388 token::BinOp(token::And) | token::AndAnd => {
3390 let m = self.parse_mutability();
3391 let e = self.parse_prefix_expr(None);
3392 let (span, e) = self.interpolated_or_expr_span(e)?;
3393 (lo.to(span), ExprKind::AddrOf(m, e))
3395 token::Ident(..) if self.token.is_keyword(keywords::In) => {
3397 let place = self.parse_expr_res(
3398 Restrictions::NO_STRUCT_LITERAL,
3401 let blk = self.parse_block()?;
3402 let span = blk.span;
3403 let blk_expr = self.mk_expr(span, ExprKind::Block(blk, None), ThinVec::new());
3404 (lo.to(span), ExprKind::ObsoleteInPlace(place, blk_expr))
3406 token::Ident(..) if self.token.is_keyword(keywords::Box) => {
3408 let e = self.parse_prefix_expr(None);
3409 let (span, e) = self.interpolated_or_expr_span(e)?;
3410 (lo.to(span), ExprKind::Box(e))
3412 token::Ident(..) if self.token.is_ident_named("not") => {
3413 // `not` is just an ordinary identifier in Rust-the-language,
3414 // but as `rustc`-the-compiler, we can issue clever diagnostics
3415 // for confused users who really want to say `!`
3416 let token_cannot_continue_expr = |t: &token::Token| match *t {
3417 // These tokens can start an expression after `!`, but
3418 // can't continue an expression after an ident
3419 token::Ident(ident, is_raw) => token::ident_can_begin_expr(ident, is_raw),
3420 token::Literal(..) | token::Pound => true,
3421 token::Interpolated(ref nt) => match **nt {
3422 token::NtIdent(..) | token::NtExpr(..) |
3423 token::NtBlock(..) | token::NtPath(..) => true,
3428 let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr);
3429 if cannot_continue_expr {
3431 // Emit the error ...
3432 let mut err = self.diagnostic()
3433 .struct_span_err(self.span,
3434 &format!("unexpected {} after identifier",
3435 self.this_token_descr()));
3436 // span the `not` plus trailing whitespace to avoid
3437 // trailing whitespace after the `!` in our suggestion
3438 let to_replace = self.sess.source_map()
3439 .span_until_non_whitespace(lo.to(self.span));
3440 err.span_suggestion_short(
3442 "use `!` to perform logical negation",
3444 Applicability::MachineApplicable
3447 // —and recover! (just as if we were in the block
3448 // for the `token::Not` arm)
3449 let e = self.parse_prefix_expr(None);
3450 let (span, e) = self.interpolated_or_expr_span(e)?;
3451 (lo.to(span), self.mk_unary(UnOp::Not, e))
3453 return self.parse_dot_or_call_expr(Some(attrs));
3456 _ => { return self.parse_dot_or_call_expr(Some(attrs)); }
3458 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
3461 /// Parses an associative expression.
3463 /// This parses an expression accounting for associativity and precedence of the operators in
3466 fn parse_assoc_expr(&mut self,
3467 already_parsed_attrs: Option<ThinVec<Attribute>>)
3468 -> PResult<'a, P<Expr>> {
3469 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
3472 /// Parses an associative expression with operators of at least `min_prec` precedence.
3473 fn parse_assoc_expr_with(&mut self,
3476 -> PResult<'a, P<Expr>> {
3477 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
3480 let attrs = match lhs {
3481 LhsExpr::AttributesParsed(attrs) => Some(attrs),
3484 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token) {
3485 return self.parse_prefix_range_expr(attrs);
3487 self.parse_prefix_expr(attrs)?
3491 if self.expr_is_complete(&lhs) {
3492 // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
3495 self.expected_tokens.push(TokenType::Operator);
3496 while let Some(op) = AssocOp::from_token(&self.token) {
3498 // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
3499 // it refers to. Interpolated identifiers are unwrapped early and never show up here
3500 // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
3501 // it as "interpolated", it doesn't change the answer for non-interpolated idents.
3502 let lhs_span = match (self.prev_token_kind, &lhs.node) {
3503 (PrevTokenKind::Interpolated, _) => self.prev_span,
3504 (PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
3505 if path.segments.len() == 1 => self.prev_span,
3509 let cur_op_span = self.span;
3510 let restrictions = if op.is_assign_like() {
3511 self.restrictions & Restrictions::NO_STRUCT_LITERAL
3515 if op.precedence() < min_prec {
3518 // Check for deprecated `...` syntax
3519 if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
3520 self.err_dotdotdot_syntax(self.span);
3524 if op.is_comparison() {
3525 self.check_no_chained_comparison(&lhs, &op);
3528 if op == AssocOp::As {
3529 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
3531 } else if op == AssocOp::Colon {
3532 let maybe_path = self.could_ascription_be_path(&lhs.node);
3533 let next_sp = self.span;
3535 lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
3538 self.bad_type_ascription(
3549 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
3550 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
3551 // generalise it to the Fixity::None code.
3553 // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
3554 // two variants are handled with `parse_prefix_range_expr` call above.
3555 let rhs = if self.is_at_start_of_range_notation_rhs() {
3556 Some(self.parse_assoc_expr_with(op.precedence() + 1,
3557 LhsExpr::NotYetParsed)?)
3561 let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
3566 let limits = if op == AssocOp::DotDot {
3567 RangeLimits::HalfOpen
3572 let r = self.mk_range(Some(lhs), rhs, limits)?;
3573 lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
3577 let rhs = match op.fixity() {
3578 Fixity::Right => self.with_res(
3579 restrictions - Restrictions::STMT_EXPR,
3581 this.parse_assoc_expr_with(op.precedence(),
3582 LhsExpr::NotYetParsed)
3584 Fixity::Left => self.with_res(
3585 restrictions - Restrictions::STMT_EXPR,
3587 this.parse_assoc_expr_with(op.precedence() + 1,
3588 LhsExpr::NotYetParsed)
3590 // We currently have no non-associative operators that are not handled above by
3591 // the special cases. The code is here only for future convenience.
3592 Fixity::None => self.with_res(
3593 restrictions - Restrictions::STMT_EXPR,
3595 this.parse_assoc_expr_with(op.precedence() + 1,
3596 LhsExpr::NotYetParsed)
3600 // Make sure that the span of the parent node is larger than the span of lhs and rhs,
3601 // including the attributes.
3605 .filter(|a| a.style == AttrStyle::Outer)
3607 .map_or(lhs_span, |a| a.span);
3608 let span = lhs_span.to(rhs.span);
3610 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
3611 AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
3612 AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
3613 AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
3614 AssocOp::Greater | AssocOp::GreaterEqual => {
3615 let ast_op = op.to_ast_binop().unwrap();
3616 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
3617 self.mk_expr(span, binary, ThinVec::new())
3620 self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
3621 AssocOp::ObsoleteInPlace =>
3622 self.mk_expr(span, ExprKind::ObsoleteInPlace(lhs, rhs), ThinVec::new()),
3623 AssocOp::AssignOp(k) => {
3625 token::Plus => BinOpKind::Add,
3626 token::Minus => BinOpKind::Sub,
3627 token::Star => BinOpKind::Mul,
3628 token::Slash => BinOpKind::Div,
3629 token::Percent => BinOpKind::Rem,
3630 token::Caret => BinOpKind::BitXor,
3631 token::And => BinOpKind::BitAnd,
3632 token::Or => BinOpKind::BitOr,
3633 token::Shl => BinOpKind::Shl,
3634 token::Shr => BinOpKind::Shr,
3636 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
3637 self.mk_expr(span, aopexpr, ThinVec::new())
3639 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
3640 self.bug("AssocOp should have been handled by special case")
3644 if op.fixity() == Fixity::None { break }
3649 fn could_ascription_be_path(&self, node: &ast::ExprKind) -> bool {
3650 self.token.is_ident() &&
3651 if let ast::ExprKind::Path(..) = node { true } else { false } &&
3652 !self.token.is_reserved_ident() && // v `foo:bar(baz)`
3653 self.look_ahead(1, |t| t == &token::OpenDelim(token::Paren)) ||
3654 self.look_ahead(1, |t| t == &token::Lt) && // `foo:bar<baz`
3655 self.look_ahead(2, |t| t.is_ident()) ||
3656 self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar:baz`
3657 self.look_ahead(2, |t| t.is_ident()) ||
3658 self.look_ahead(1, |t| t == &token::ModSep) && // `foo:bar::baz`
3659 self.look_ahead(2, |t| t.is_ident())
3662 fn bad_type_ascription(
3664 err: &mut DiagnosticBuilder<'a>,
3670 err.span_label(self.span, "expecting a type here because of type ascription");
3671 let cm = self.sess.source_map();
3672 let next_pos = cm.lookup_char_pos(next_sp.lo());
3673 let op_pos = cm.lookup_char_pos(cur_op_span.hi());
3674 if op_pos.line != next_pos.line {
3675 err.span_suggestion(
3677 "try using a semicolon",
3679 Applicability::MaybeIncorrect,
3683 err.span_suggestion(
3685 "maybe you meant to write a path separator here",
3687 Applicability::MaybeIncorrect,
3690 err.note("type ascription is a nightly-only feature that lets \
3691 you annotate an expression with a type: `<expr>: <type>`");
3694 "this expression expects an ascribed type after the colon",
3696 err.help("this might be indicative of a syntax error elsewhere");
3701 fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
3702 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
3703 -> PResult<'a, P<Expr>> {
3704 let mk_expr = |this: &mut Self, rhs: P<Ty>| {
3705 this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
3708 // Save the state of the parser before parsing type normally, in case there is a
3709 // LessThan comparison after this cast.
3710 let parser_snapshot_before_type = self.clone();
3711 match self.parse_ty_no_plus() {
3713 Ok(mk_expr(self, rhs))
3715 Err(mut type_err) => {
3716 // Rewind to before attempting to parse the type with generics, to recover
3717 // from situations like `x as usize < y` in which we first tried to parse
3718 // `usize < y` as a type with generic arguments.
3719 let parser_snapshot_after_type = self.clone();
3720 mem::replace(self, parser_snapshot_before_type);
3722 match self.parse_path(PathStyle::Expr) {
3724 let (op_noun, op_verb) = match self.token {
3725 token::Lt => ("comparison", "comparing"),
3726 token::BinOp(token::Shl) => ("shift", "shifting"),
3728 // We can end up here even without `<` being the next token, for
3729 // example because `parse_ty_no_plus` returns `Err` on keywords,
3730 // but `parse_path` returns `Ok` on them due to error recovery.
3731 // Return original error and parser state.
3732 mem::replace(self, parser_snapshot_after_type);
3733 return Err(type_err);
3737 // Successfully parsed the type path leaving a `<` yet to parse.
3740 // Report non-fatal diagnostics, keep `x as usize` as an expression
3741 // in AST and continue parsing.
3742 let msg = format!("`<` is interpreted as a start of generic \
3743 arguments for `{}`, not a {}", path, op_noun);
3744 let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg);
3745 err.span_label(self.look_ahead_span(1).to(parser_snapshot_after_type.span),
3746 "interpreted as generic arguments");
3747 err.span_label(self.span, format!("not interpreted as {}", op_noun));
3749 let expr = mk_expr(self, P(Ty {
3751 node: TyKind::Path(None, path),
3752 id: ast::DUMMY_NODE_ID
3755 let expr_str = self.sess.source_map().span_to_snippet(expr.span)
3756 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
3757 err.span_suggestion(
3759 &format!("try {} the cast value", op_verb),
3760 format!("({})", expr_str),
3761 Applicability::MachineApplicable
3767 Err(mut path_err) => {
3768 // Couldn't parse as a path, return original error and parser state.
3770 mem::replace(self, parser_snapshot_after_type);
3778 /// Produce an error if comparison operators are chained (RFC #558).
3779 /// We only need to check lhs, not rhs, because all comparison ops
3780 /// have same precedence and are left-associative
3781 fn check_no_chained_comparison(&mut self, lhs: &Expr, outer_op: &AssocOp) {
3782 debug_assert!(outer_op.is_comparison(),
3783 "check_no_chained_comparison: {:?} is not comparison",
3786 ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
3787 // respan to include both operators
3788 let op_span = op.span.to(self.span);
3789 let mut err = self.diagnostic().struct_span_err(op_span,
3790 "chained comparison operators require parentheses");
3791 if op.node == BinOpKind::Lt &&
3792 *outer_op == AssocOp::Less || // Include `<` to provide this recommendation
3793 *outer_op == AssocOp::Greater // even in a case like the following:
3794 { // Foo<Bar<Baz<Qux, ()>>>
3796 "use `::<...>` instead of `<...>` if you meant to specify type arguments");
3797 err.help("or use `(...)` if you meant to specify fn arguments");
3805 /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
3806 fn parse_prefix_range_expr(&mut self,
3807 already_parsed_attrs: Option<ThinVec<Attribute>>)
3808 -> PResult<'a, P<Expr>> {
3809 // Check for deprecated `...` syntax
3810 if self.token == token::DotDotDot {
3811 self.err_dotdotdot_syntax(self.span);
3814 debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token),
3815 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
3817 let tok = self.token.clone();
3818 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
3820 let mut hi = self.span;
3822 let opt_end = if self.is_at_start_of_range_notation_rhs() {
3823 // RHS must be parsed with more associativity than the dots.
3824 let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
3825 Some(self.parse_assoc_expr_with(next_prec,
3826 LhsExpr::NotYetParsed)
3834 let limits = if tok == token::DotDot {
3835 RangeLimits::HalfOpen
3840 let r = self.mk_range(None, opt_end, limits)?;
3841 Ok(self.mk_expr(lo.to(hi), r, attrs))
3844 fn is_at_start_of_range_notation_rhs(&self) -> bool {
3845 if self.token.can_begin_expr() {
3846 // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
3847 if self.token == token::OpenDelim(token::Brace) {
3848 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
3856 /// Parses an `if` or `if let` expression (`if` token already eaten).
3857 fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3858 if self.check_keyword(keywords::Let) {
3859 return self.parse_if_let_expr(attrs);
3861 let lo = self.prev_span;
3862 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3864 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
3865 // verify that the last statement is either an implicit return (no `;`) or an explicit
3866 // return. This won't catch blocks with an explicit `return`, but that would be caught by
3867 // the dead code lint.
3868 if self.eat_keyword(keywords::Else) || !cond.returns() {
3869 let sp = self.sess.source_map().next_point(lo);
3870 let mut err = self.diagnostic()
3871 .struct_span_err(sp, "missing condition for `if` statemement");
3872 err.span_label(sp, "expected if condition here");
3875 let not_block = self.token != token::OpenDelim(token::Brace);
3876 let thn = self.parse_block().map_err(|mut err| {
3878 err.span_label(lo, "this `if` statement has a condition, but no block");
3882 let mut els: Option<P<Expr>> = None;
3883 let mut hi = thn.span;
3884 if self.eat_keyword(keywords::Else) {
3885 let elexpr = self.parse_else_expr()?;
3889 Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
3892 /// Parses an `if let` expression (`if` token already eaten).
3893 fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>)
3894 -> PResult<'a, P<Expr>> {
3895 let lo = self.prev_span;
3896 self.expect_keyword(keywords::Let)?;
3897 let pats = self.parse_pats()?;
3898 self.expect(&token::Eq)?;
3899 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3900 let thn = self.parse_block()?;
3901 let (hi, els) = if self.eat_keyword(keywords::Else) {
3902 let expr = self.parse_else_expr()?;
3903 (expr.span, Some(expr))
3907 Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pats, expr, thn, els), attrs))
3910 /// Parses `move |args| expr`.
3911 fn parse_lambda_expr(&mut self,
3912 attrs: ThinVec<Attribute>)
3913 -> PResult<'a, P<Expr>>
3916 let movability = if self.eat_keyword(keywords::Static) {
3921 let asyncness = if self.span.rust_2018() {
3922 self.parse_asyncness()
3926 let capture_clause = if self.eat_keyword(keywords::Move) {
3931 let decl = self.parse_fn_block_decl()?;
3932 let decl_hi = self.prev_span;
3933 let body = match decl.output {
3934 FunctionRetTy::Default(_) => {
3935 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
3936 self.parse_expr_res(restrictions, None)?
3939 // If an explicit return type is given, require a
3940 // block to appear (RFC 968).
3941 let body_lo = self.span;
3942 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
3948 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
3952 // `else` token already eaten
3953 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
3954 if self.eat_keyword(keywords::If) {
3955 return self.parse_if_expr(ThinVec::new());
3957 let blk = self.parse_block()?;
3958 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new()));
3962 /// Parse a 'for' .. 'in' expression ('for' token already eaten)
3963 fn parse_for_expr(&mut self, opt_label: Option<Label>,
3965 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3966 // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
3968 let pat = self.parse_top_level_pat()?;
3969 if !self.eat_keyword(keywords::In) {
3970 let in_span = self.prev_span.between(self.span);
3971 let mut err = self.sess.span_diagnostic
3972 .struct_span_err(in_span, "missing `in` in `for` loop");
3973 err.span_suggestion_short(
3974 in_span, "try adding `in` here", " in ".into(),
3975 // has been misleading, at least in the past (closed Issue #48492)
3976 Applicability::MaybeIncorrect
3980 let in_span = self.prev_span;
3981 if self.eat_keyword(keywords::In) {
3982 // a common typo: `for _ in in bar {}`
3983 let mut err = self.sess.span_diagnostic.struct_span_err(
3985 "expected iterable, found keyword `in`",
3987 err.span_suggestion_short(
3988 in_span.until(self.prev_span),
3989 "remove the duplicated `in`",
3991 Applicability::MachineApplicable,
3993 err.note("if you meant to use emplacement syntax, it is obsolete (for now, anyway)");
3994 err.note("for more information on the status of emplacement syntax, see <\
3995 https://github.com/rust-lang/rust/issues/27779#issuecomment-378416911>");
3998 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3999 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
4000 attrs.extend(iattrs);
4002 let hi = self.prev_span;
4003 Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs))
4006 /// Parses a `while` or `while let` expression (`while` token already eaten).
4007 fn parse_while_expr(&mut self, opt_label: Option<Label>,
4009 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
4010 if self.token.is_keyword(keywords::Let) {
4011 return self.parse_while_let_expr(opt_label, span_lo, attrs);
4013 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
4014 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
4015 attrs.extend(iattrs);
4016 let span = span_lo.to(body.span);
4017 return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs));
4020 /// Parses a `while let` expression (`while` token already eaten).
4021 fn parse_while_let_expr(&mut self, opt_label: Option<Label>,
4023 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
4024 self.expect_keyword(keywords::Let)?;
4025 let pats = self.parse_pats()?;
4026 self.expect(&token::Eq)?;
4027 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
4028 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
4029 attrs.extend(iattrs);
4030 let span = span_lo.to(body.span);
4031 return Ok(self.mk_expr(span, ExprKind::WhileLet(pats, expr, body, opt_label), attrs));
4034 // parse `loop {...}`, `loop` token already eaten
4035 fn parse_loop_expr(&mut self, opt_label: Option<Label>,
4037 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
4038 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
4039 attrs.extend(iattrs);
4040 let span = span_lo.to(body.span);
4041 Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
4044 /// Parses an `async move {...}` expression.
4045 pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>)
4046 -> PResult<'a, P<Expr>>
4048 let span_lo = self.span;
4049 self.expect_keyword(keywords::Async)?;
4050 let capture_clause = if self.eat_keyword(keywords::Move) {
4055 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
4056 attrs.extend(iattrs);
4058 span_lo.to(body.span),
4059 ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs))
4062 /// Parses a `try {...}` expression (`try` token already eaten).
4063 fn parse_try_block(&mut self, span_lo: Span, mut attrs: ThinVec<Attribute>)
4064 -> PResult<'a, P<Expr>>
4066 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
4067 attrs.extend(iattrs);
4068 Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
4071 // `match` token already eaten
4072 fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
4073 let match_span = self.prev_span;
4074 let lo = self.prev_span;
4075 let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL,
4077 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
4078 if self.token == token::Token::Semi {
4079 e.span_suggestion_short(
4081 "try removing this `match`",
4083 Applicability::MaybeIncorrect // speculative
4088 attrs.extend(self.parse_inner_attributes()?);
4090 let mut arms: Vec<Arm> = Vec::new();
4091 while self.token != token::CloseDelim(token::Brace) {
4092 match self.parse_arm() {
4093 Ok(arm) => arms.push(arm),
4095 // Recover by skipping to the end of the block.
4097 self.recover_stmt();
4098 let span = lo.to(self.span);
4099 if self.token == token::CloseDelim(token::Brace) {
4102 return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
4108 return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
4111 crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
4112 maybe_whole!(self, NtArm, |x| x);
4114 let attrs = self.parse_outer_attributes()?;
4115 let pats = self.parse_pats()?;
4116 let guard = if self.eat_keyword(keywords::If) {
4117 Some(Guard::If(self.parse_expr()?))
4121 let arrow_span = self.span;
4122 self.expect(&token::FatArrow)?;
4123 let arm_start_span = self.span;
4125 let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
4126 .map_err(|mut err| {
4127 err.span_label(arrow_span, "while parsing the `match` arm starting here");
4131 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
4132 && self.token != token::CloseDelim(token::Brace);
4135 let cm = self.sess.source_map();
4136 self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])
4137 .map_err(|mut err| {
4138 match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
4139 (Ok(ref expr_lines), Ok(ref arm_start_lines))
4140 if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
4141 && expr_lines.lines.len() == 2
4142 && self.token == token::FatArrow => {
4143 // We check whether there's any trailing code in the parse span,
4144 // if there isn't, we very likely have the following:
4147 // | -- - missing comma
4153 // | parsed until here as `"y" & X`
4154 err.span_suggestion_short(
4155 cm.next_point(arm_start_span),
4156 "missing a comma here to end this `match` arm",
4158 Applicability::MachineApplicable
4162 err.span_label(arrow_span,
4163 "while parsing the `match` arm starting here");
4169 self.eat(&token::Comma);
4180 /// Parses an expression.
4182 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
4183 self.parse_expr_res(Restrictions::empty(), None)
4186 /// Evaluates the closure with restrictions in place.
4188 /// Afters the closure is evaluated, restrictions are reset.
4189 fn with_res<F, T>(&mut self, r: Restrictions, f: F) -> T
4190 where F: FnOnce(&mut Self) -> T
4192 let old = self.restrictions;
4193 self.restrictions = r;
4195 self.restrictions = old;
4200 /// Parses an expression, subject to the given restrictions.
4202 fn parse_expr_res(&mut self, r: Restrictions,
4203 already_parsed_attrs: Option<ThinVec<Attribute>>)
4204 -> PResult<'a, P<Expr>> {
4205 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
4208 /// Parses the RHS of a local variable declaration (e.g., '= 14;').
4209 fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
4210 if self.eat(&token::Eq) {
4211 Ok(Some(self.parse_expr()?))
4213 Ok(Some(self.parse_expr()?))
4219 /// Parses patterns, separated by '|' s.
4220 fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
4221 // Allow a '|' before the pats (RFC 1925 + RFC 2530)
4222 self.eat(&token::BinOp(token::Or));
4224 let mut pats = Vec::new();
4226 pats.push(self.parse_top_level_pat()?);
4228 if self.token == token::OrOr {
4229 let mut err = self.struct_span_err(self.span,
4230 "unexpected token `||` after pattern");
4231 err.span_suggestion(
4233 "use a single `|` to specify multiple patterns",
4235 Applicability::MachineApplicable
4239 } else if self.eat(&token::BinOp(token::Or)) {
4240 // This is a No-op. Continue the loop to parse the next
4248 // Parses a parenthesized list of patterns like
4249 // `()`, `(p)`, `(p,)`, `(p, q)`, or `(p, .., q)`. Returns:
4250 // - a vector of the patterns that were parsed
4251 // - an option indicating the index of the `..` element
4252 // - a boolean indicating whether a trailing comma was present.
4253 // Trailing commas are significant because (p) and (p,) are different patterns.
4254 fn parse_parenthesized_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
4255 self.expect(&token::OpenDelim(token::Paren))?;
4256 let result = self.parse_pat_list()?;
4257 self.expect(&token::CloseDelim(token::Paren))?;
4261 fn parse_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
4262 let mut fields = Vec::new();
4263 let mut ddpos = None;
4264 let mut prev_dd_sp = None;
4265 let mut trailing_comma = false;
4267 if self.eat(&token::DotDot) {
4268 if ddpos.is_none() {
4269 ddpos = Some(fields.len());
4270 prev_dd_sp = Some(self.prev_span);
4272 // Emit a friendly error, ignore `..` and continue parsing
4273 let mut err = self.struct_span_err(
4275 "`..` can only be used once per tuple or tuple struct pattern",
4277 err.span_label(self.prev_span, "can only be used once per pattern");
4278 if let Some(sp) = prev_dd_sp {
4279 err.span_label(sp, "previously present here");
4283 } else if !self.check(&token::CloseDelim(token::Paren)) {
4284 fields.push(self.parse_pat(None)?);
4289 trailing_comma = self.eat(&token::Comma);
4290 if !trailing_comma {
4295 if ddpos == Some(fields.len()) && trailing_comma {
4296 // `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
4297 let msg = "trailing comma is not permitted after `..`";
4298 self.struct_span_err(self.prev_span, msg)
4299 .span_label(self.prev_span, msg)
4303 Ok((fields, ddpos, trailing_comma))
4306 fn parse_pat_vec_elements(
4308 ) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
4309 let mut before = Vec::new();
4310 let mut slice = None;
4311 let mut after = Vec::new();
4312 let mut first = true;
4313 let mut before_slice = true;
4315 while self.token != token::CloseDelim(token::Bracket) {
4319 self.expect(&token::Comma)?;
4321 if self.token == token::CloseDelim(token::Bracket)
4322 && (before_slice || !after.is_empty()) {
4328 if self.eat(&token::DotDot) {
4330 if self.check(&token::Comma) ||
4331 self.check(&token::CloseDelim(token::Bracket)) {
4332 slice = Some(P(Pat {
4333 id: ast::DUMMY_NODE_ID,
4334 node: PatKind::Wild,
4335 span: self.prev_span,
4337 before_slice = false;
4343 let subpat = self.parse_pat(None)?;
4344 if before_slice && self.eat(&token::DotDot) {
4345 slice = Some(subpat);
4346 before_slice = false;
4347 } else if before_slice {
4348 before.push(subpat);
4354 Ok((before, slice, after))
4360 attrs: Vec<Attribute>
4361 ) -> PResult<'a, source_map::Spanned<ast::FieldPat>> {
4362 // Check if a colon exists one ahead. This means we're parsing a fieldname.
4364 let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
4365 // Parsing a pattern of the form "fieldname: pat"
4366 let fieldname = self.parse_field_name()?;
4368 let pat = self.parse_pat(None)?;
4370 (pat, fieldname, false)
4372 // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
4373 let is_box = self.eat_keyword(keywords::Box);
4374 let boxed_span = self.span;
4375 let is_ref = self.eat_keyword(keywords::Ref);
4376 let is_mut = self.eat_keyword(keywords::Mut);
4377 let fieldname = self.parse_ident()?;
4378 hi = self.prev_span;
4380 let bind_type = match (is_ref, is_mut) {
4381 (true, true) => BindingMode::ByRef(Mutability::Mutable),
4382 (true, false) => BindingMode::ByRef(Mutability::Immutable),
4383 (false, true) => BindingMode::ByValue(Mutability::Mutable),
4384 (false, false) => BindingMode::ByValue(Mutability::Immutable),
4386 let fieldpat = P(Pat {
4387 id: ast::DUMMY_NODE_ID,
4388 node: PatKind::Ident(bind_type, fieldname, None),
4389 span: boxed_span.to(hi),
4392 let subpat = if is_box {
4394 id: ast::DUMMY_NODE_ID,
4395 node: PatKind::Box(fieldpat),
4401 (subpat, fieldname, true)
4404 Ok(source_map::Spanned {
4406 node: ast::FieldPat {
4410 attrs: attrs.into(),
4415 /// Parses the fields of a struct-like pattern.
4416 fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<source_map::Spanned<ast::FieldPat>>, bool)> {
4417 let mut fields = Vec::new();
4418 let mut etc = false;
4419 let mut ate_comma = true;
4420 let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
4421 let mut etc_span = None;
4423 while self.token != token::CloseDelim(token::Brace) {
4424 let attrs = self.parse_outer_attributes()?;
4427 // check that a comma comes after every field
4429 let err = self.struct_span_err(self.prev_span, "expected `,`");
4430 if let Some(mut delayed) = delayed_err {
4437 if self.check(&token::DotDot) || self.token == token::DotDotDot {
4439 let mut etc_sp = self.span;
4441 if self.token == token::DotDotDot { // Issue #46718
4442 // Accept `...` as if it were `..` to avoid further errors
4443 let mut err = self.struct_span_err(self.span,
4444 "expected field pattern, found `...`");
4445 err.span_suggestion(
4447 "to omit remaining fields, use one fewer `.`",
4449 Applicability::MachineApplicable
4453 self.bump(); // `..` || `...`
4455 if self.token == token::CloseDelim(token::Brace) {
4456 etc_span = Some(etc_sp);
4459 let token_str = self.this_token_descr();
4460 let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
4462 err.span_label(self.span, "expected `}`");
4463 let mut comma_sp = None;
4464 if self.token == token::Comma { // Issue #49257
4465 etc_sp = etc_sp.to(self.sess.source_map().span_until_non_whitespace(self.span));
4466 err.span_label(etc_sp,
4467 "`..` must be at the end and cannot have a trailing comma");
4468 comma_sp = Some(self.span);
4473 etc_span = Some(etc_sp.until(self.span));
4474 if self.token == token::CloseDelim(token::Brace) {
4475 // If the struct looks otherwise well formed, recover and continue.
4476 if let Some(sp) = comma_sp {
4477 err.span_suggestion_short(
4479 "remove this comma",
4481 Applicability::MachineApplicable,
4486 } else if self.token.is_ident() && ate_comma {
4487 // Accept fields coming after `..,`.
4488 // This way we avoid "pattern missing fields" errors afterwards.
4489 // We delay this error until the end in order to have a span for a
4491 if let Some(mut delayed_err) = delayed_err {
4495 delayed_err = Some(err);
4498 if let Some(mut err) = delayed_err {
4505 fields.push(match self.parse_pat_field(lo, attrs) {
4508 if let Some(mut delayed_err) = delayed_err {
4514 ate_comma = self.eat(&token::Comma);
4517 if let Some(mut err) = delayed_err {
4518 if let Some(etc_span) = etc_span {
4519 err.multipart_suggestion(
4520 "move the `..` to the end of the field list",
4522 (etc_span, String::new()),
4523 (self.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
4525 Applicability::MachineApplicable,
4530 return Ok((fields, etc));
4533 fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
4534 if self.token.is_path_start() {
4536 let (qself, path) = if self.eat_lt() {
4537 // Parse a qualified path
4538 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
4541 // Parse an unqualified path
4542 (None, self.parse_path(PathStyle::Expr)?)
4544 let hi = self.prev_span;
4545 Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
4547 self.parse_literal_maybe_minus()
4551 // helper function to decide whether to parse as ident binding or to try to do
4552 // something more complex like range patterns
4553 fn parse_as_ident(&mut self) -> bool {
4554 self.look_ahead(1, |t| match *t {
4555 token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
4556 token::DotDotDot | token::DotDotEq | token::ModSep | token::Not => Some(false),
4557 // ensure slice patterns [a, b.., c] and [a, b, c..] don't go into the
4558 // range pattern branch
4559 token::DotDot => None,
4561 }).unwrap_or_else(|| self.look_ahead(2, |t| match *t {
4562 token::Comma | token::CloseDelim(token::Bracket) => true,
4567 /// A wrapper around `parse_pat` with some special error handling for the
4568 /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
4569 /// to subpatterns within such).
4570 fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
4571 let pat = self.parse_pat(None)?;
4572 if self.token == token::Comma {
4573 // An unexpected comma after a top-level pattern is a clue that the
4574 // user (perhaps more accustomed to some other language) forgot the
4575 // parentheses in what should have been a tuple pattern; return a
4576 // suggestion-enhanced error here rather than choking on the comma
4578 let comma_span = self.span;
4580 if let Err(mut err) = self.parse_pat_list() {
4581 // We didn't expect this to work anyway; we just wanted
4582 // to advance to the end of the comma-sequence so we know
4583 // the span to suggest parenthesizing
4586 let seq_span = pat.span.to(self.prev_span);
4587 let mut err = self.struct_span_err(comma_span,
4588 "unexpected `,` in pattern");
4589 if let Ok(seq_snippet) = self.sess.source_map().span_to_snippet(seq_span) {
4590 err.span_suggestion(
4592 "try adding parentheses to match on a tuple..",
4593 format!("({})", seq_snippet),
4594 Applicability::MachineApplicable
4597 "..or a vertical bar to match on multiple alternatives",
4598 format!("{}", seq_snippet.replace(",", " |")),
4599 Applicability::MachineApplicable
4607 /// Parses a pattern.
4608 pub fn parse_pat(&mut self, expected: Option<&'static str>) -> PResult<'a, P<Pat>> {
4609 self.parse_pat_with_range_pat(true, expected)
4612 /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
4614 fn parse_pat_with_range_pat(
4616 allow_range_pat: bool,
4617 expected: Option<&'static str>,
4618 ) -> PResult<'a, P<Pat>> {
4619 maybe_recover_from_interpolated_ty_qpath!(self, true);
4620 maybe_whole!(self, NtPat, |x| x);
4625 token::BinOp(token::And) | token::AndAnd => {
4626 // Parse &pat / &mut pat
4628 let mutbl = self.parse_mutability();
4629 if let token::Lifetime(ident) = self.token {
4630 let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern",
4632 err.span_label(self.span, "unexpected lifetime");
4635 let subpat = self.parse_pat_with_range_pat(false, expected)?;
4636 pat = PatKind::Ref(subpat, mutbl);
4638 token::OpenDelim(token::Paren) => {
4639 // Parse (pat,pat,pat,...) as tuple pattern
4640 let (fields, ddpos, trailing_comma) = self.parse_parenthesized_pat_list()?;
4641 pat = if fields.len() == 1 && ddpos.is_none() && !trailing_comma {
4642 PatKind::Paren(fields.into_iter().nth(0).unwrap())
4644 PatKind::Tuple(fields, ddpos)
4647 token::OpenDelim(token::Bracket) => {
4648 // Parse [pat,pat,...] as slice pattern
4650 let (before, slice, after) = self.parse_pat_vec_elements()?;
4651 self.expect(&token::CloseDelim(token::Bracket))?;
4652 pat = PatKind::Slice(before, slice, after);
4654 // At this point, token != &, &&, (, [
4655 _ => if self.eat_keyword(keywords::Underscore) {
4657 pat = PatKind::Wild;
4658 } else if self.eat_keyword(keywords::Mut) {
4659 // Parse mut ident @ pat / mut ref ident @ pat
4660 let mutref_span = self.prev_span.to(self.span);
4661 let binding_mode = if self.eat_keyword(keywords::Ref) {
4663 .struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
4666 "try switching the order",
4668 Applicability::MachineApplicable
4670 BindingMode::ByRef(Mutability::Mutable)
4672 BindingMode::ByValue(Mutability::Mutable)
4674 pat = self.parse_pat_ident(binding_mode)?;
4675 } else if self.eat_keyword(keywords::Ref) {
4676 // Parse ref ident @ pat / ref mut ident @ pat
4677 let mutbl = self.parse_mutability();
4678 pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?;
4679 } else if self.eat_keyword(keywords::Box) {
4681 let subpat = self.parse_pat_with_range_pat(false, None)?;
4682 pat = PatKind::Box(subpat);
4683 } else if self.token.is_ident() && !self.token.is_reserved_ident() &&
4684 self.parse_as_ident() {
4685 // Parse ident @ pat
4686 // This can give false positives and parse nullary enums,
4687 // they are dealt with later in resolve
4688 let binding_mode = BindingMode::ByValue(Mutability::Immutable);
4689 pat = self.parse_pat_ident(binding_mode)?;
4690 } else if self.token.is_path_start() {
4691 // Parse pattern starting with a path
4692 let (qself, path) = if self.eat_lt() {
4693 // Parse a qualified path
4694 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
4697 // Parse an unqualified path
4698 (None, self.parse_path(PathStyle::Expr)?)
4701 token::Not if qself.is_none() => {
4702 // Parse macro invocation
4704 let (delim, tts) = self.expect_delimited_token_tree()?;
4705 let mac = respan(lo.to(self.prev_span), Mac_ { path, tts, delim });
4706 pat = PatKind::Mac(mac);
4708 token::DotDotDot | token::DotDotEq | token::DotDot => {
4709 let end_kind = match self.token {
4710 token::DotDot => RangeEnd::Excluded,
4711 token::DotDotDot => RangeEnd::Included(RangeSyntax::DotDotDot),
4712 token::DotDotEq => RangeEnd::Included(RangeSyntax::DotDotEq),
4713 _ => panic!("can only parse `..`/`...`/`..=` for ranges \
4716 let op_span = self.span;
4718 let span = lo.to(self.prev_span);
4719 let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
4721 let end = self.parse_pat_range_end()?;
4722 let op = Spanned { span: op_span, node: end_kind };
4723 pat = PatKind::Range(begin, end, op);
4725 token::OpenDelim(token::Brace) => {
4726 if qself.is_some() {
4727 let msg = "unexpected `{` after qualified path";
4728 let mut err = self.fatal(msg);
4729 err.span_label(self.span, msg);
4732 // Parse struct pattern
4734 let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
4736 self.recover_stmt();
4740 pat = PatKind::Struct(path, fields, etc);
4742 token::OpenDelim(token::Paren) => {
4743 if qself.is_some() {
4744 let msg = "unexpected `(` after qualified path";
4745 let mut err = self.fatal(msg);
4746 err.span_label(self.span, msg);
4749 // Parse tuple struct or enum pattern
4750 let (fields, ddpos, _) = self.parse_parenthesized_pat_list()?;
4751 pat = PatKind::TupleStruct(path, fields, ddpos)
4753 _ => pat = PatKind::Path(qself, path),
4756 // Try to parse everything else as literal with optional minus
4757 match self.parse_literal_maybe_minus() {
4759 let op_span = self.span;
4760 if self.check(&token::DotDot) || self.check(&token::DotDotEq) ||
4761 self.check(&token::DotDotDot) {
4762 let end_kind = if self.eat(&token::DotDotDot) {
4763 RangeEnd::Included(RangeSyntax::DotDotDot)
4764 } else if self.eat(&token::DotDotEq) {
4765 RangeEnd::Included(RangeSyntax::DotDotEq)
4766 } else if self.eat(&token::DotDot) {
4769 panic!("impossible case: we already matched \
4770 on a range-operator token")
4772 let end = self.parse_pat_range_end()?;
4773 let op = Spanned { span: op_span, node: end_kind };
4774 pat = PatKind::Range(begin, end, op);
4776 pat = PatKind::Lit(begin);
4780 self.cancel(&mut err);
4781 let expected = expected.unwrap_or("pattern");
4783 "expected {}, found {}",
4785 self.this_token_descr(),
4787 let mut err = self.fatal(&msg);
4788 err.span_label(self.span, format!("expected {}", expected));
4795 let pat = P(Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID });
4796 let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
4798 if !allow_range_pat {
4801 _, _, Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
4803 PatKind::Range(..) => {
4804 let mut err = self.struct_span_err(
4806 "the range pattern here has ambiguous interpretation",
4808 err.span_suggestion(
4810 "add parentheses to clarify the precedence",
4811 format!("({})", pprust::pat_to_string(&pat)),
4812 // "ambiguous interpretation" implies that we have to be guessing
4813 Applicability::MaybeIncorrect
4824 /// Parses `ident` or `ident @ pat`.
4825 /// used by the copy foo and ref foo patterns to give a good
4826 /// error message when parsing mistakes like `ref foo(a, b)`.
4827 fn parse_pat_ident(&mut self,
4828 binding_mode: ast::BindingMode)
4829 -> PResult<'a, PatKind> {
4830 let ident = self.parse_ident()?;
4831 let sub = if self.eat(&token::At) {
4832 Some(self.parse_pat(Some("binding pattern"))?)
4837 // just to be friendly, if they write something like
4839 // we end up here with ( as the current token. This shortly
4840 // leads to a parse error. Note that if there is no explicit
4841 // binding mode then we do not end up here, because the lookahead
4842 // will direct us over to parse_enum_variant()
4843 if self.token == token::OpenDelim(token::Paren) {
4844 return Err(self.span_fatal(
4846 "expected identifier, found enum pattern"))
4849 Ok(PatKind::Ident(binding_mode, ident, sub))
4852 /// Parses a local variable declaration.
4853 fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
4854 let lo = self.prev_span;
4855 let pat = self.parse_top_level_pat()?;
4857 let (err, ty) = if self.eat(&token::Colon) {
4858 // Save the state of the parser before parsing type normally, in case there is a `:`
4859 // instead of an `=` typo.
4860 let parser_snapshot_before_type = self.clone();
4861 let colon_sp = self.prev_span;
4862 match self.parse_ty() {
4863 Ok(ty) => (None, Some(ty)),
4865 // Rewind to before attempting to parse the type and continue parsing
4866 let parser_snapshot_after_type = self.clone();
4867 mem::replace(self, parser_snapshot_before_type);
4869 let snippet = self.sess.source_map().span_to_snippet(pat.span).unwrap();
4870 err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
4871 (Some((parser_snapshot_after_type, colon_sp, err)), None)
4877 let init = match (self.parse_initializer(err.is_some()), err) {
4878 (Ok(init), None) => { // init parsed, ty parsed
4881 (Ok(init), Some((_, colon_sp, mut err))) => { // init parsed, ty error
4882 // Could parse the type as if it were the initializer, it is likely there was a
4883 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
4884 err.span_suggestion_short(
4886 "use `=` if you meant to assign",
4888 Applicability::MachineApplicable
4891 // As this was parsed successfully, continue as if the code has been fixed for the
4892 // rest of the file. It will still fail due to the emitted error, but we avoid
4896 (Err(mut init_err), Some((snapshot, _, ty_err))) => { // init error, ty error
4898 // Couldn't parse the type nor the initializer, only raise the type error and
4899 // return to the parser state before parsing the type as the initializer.
4900 // let x: <parse_error>;
4901 mem::replace(self, snapshot);
4904 (Err(err), None) => { // init error, ty parsed
4905 // Couldn't parse the initializer and we're not attempting to recover a failed
4906 // parse of the type, return the error.
4910 let hi = if self.token == token::Semi {
4919 id: ast::DUMMY_NODE_ID,
4925 /// Parses a structure field.
4926 fn parse_name_and_ty(&mut self,
4929 attrs: Vec<Attribute>)
4930 -> PResult<'a, StructField> {
4931 let name = self.parse_ident()?;
4932 self.expect(&token::Colon)?;
4933 let ty = self.parse_ty()?;
4935 span: lo.to(self.prev_span),
4938 id: ast::DUMMY_NODE_ID,
4944 /// Emits an expected-item-after-attributes error.
4945 fn expected_item_err(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
4946 let message = match attrs.last() {
4947 Some(&Attribute { is_sugared_doc: true, .. }) => "expected item after doc comment",
4948 _ => "expected item after attributes",
4951 let mut err = self.diagnostic().struct_span_err(self.prev_span, message);
4952 if attrs.last().unwrap().is_sugared_doc {
4953 err.span_label(self.prev_span, "this doc comment doesn't document anything");
4958 /// Parse a statement. This stops just before trailing semicolons on everything but items.
4959 /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
4960 pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
4961 Ok(self.parse_stmt_(true))
4964 // Eat tokens until we can be relatively sure we reached the end of the
4965 // statement. This is something of a best-effort heuristic.
4967 // We terminate when we find an unmatched `}` (without consuming it).
4968 fn recover_stmt(&mut self) {
4969 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
4972 // If `break_on_semi` is `Break`, then we will stop consuming tokens after
4973 // finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
4974 // approximate - it can mean we break too early due to macros, but that
4975 // should only lead to sub-optimal recovery, not inaccurate parsing).
4977 // If `break_on_block` is `Break`, then we will stop consuming tokens
4978 // after finding (and consuming) a brace-delimited block.
4979 fn recover_stmt_(&mut self, break_on_semi: SemiColonMode, break_on_block: BlockMode) {
4980 let mut brace_depth = 0;
4981 let mut bracket_depth = 0;
4982 let mut in_block = false;
4983 debug!("recover_stmt_ enter loop (semi={:?}, block={:?})",
4984 break_on_semi, break_on_block);
4986 debug!("recover_stmt_ loop {:?}", self.token);
4988 token::OpenDelim(token::DelimToken::Brace) => {
4991 if break_on_block == BlockMode::Break &&
4993 bracket_depth == 0 {
4997 token::OpenDelim(token::DelimToken::Bracket) => {
5001 token::CloseDelim(token::DelimToken::Brace) => {
5002 if brace_depth == 0 {
5003 debug!("recover_stmt_ return - close delim {:?}", self.token);
5008 if in_block && bracket_depth == 0 && brace_depth == 0 {
5009 debug!("recover_stmt_ return - block end {:?}", self.token);
5013 token::CloseDelim(token::DelimToken::Bracket) => {
5015 if bracket_depth < 0 {
5021 debug!("recover_stmt_ return - Eof");
5026 if break_on_semi == SemiColonMode::Break &&
5028 bracket_depth == 0 {
5029 debug!("recover_stmt_ return - Semi");
5034 if break_on_semi == SemiColonMode::Comma &&
5036 bracket_depth == 0 {
5037 debug!("recover_stmt_ return - Semi");
5050 fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> {
5051 self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| {
5053 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
5058 fn is_async_block(&mut self) -> bool {
5059 self.token.is_keyword(keywords::Async) &&
5062 self.look_ahead(1, |t| t.is_keyword(keywords::Move)) &&
5063 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
5065 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
5070 fn is_async_fn(&mut self) -> bool {
5071 self.token.is_keyword(keywords::Async) &&
5072 self.look_ahead(1, |t| t.is_keyword(keywords::Fn))
5075 fn is_do_catch_block(&mut self) -> bool {
5076 self.token.is_keyword(keywords::Do) &&
5077 self.look_ahead(1, |t| t.is_keyword(keywords::Catch)) &&
5078 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
5079 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
5082 fn is_try_block(&mut self) -> bool {
5083 self.token.is_keyword(keywords::Try) &&
5084 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
5085 self.span.rust_2018() &&
5086 // prevent `while try {} {}`, `if try {} {} else {}`, etc.
5087 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
5090 fn is_union_item(&self) -> bool {
5091 self.token.is_keyword(keywords::Union) &&
5092 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
5095 fn is_crate_vis(&self) -> bool {
5096 self.token.is_keyword(keywords::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
5099 fn is_existential_type_decl(&self) -> bool {
5100 self.token.is_keyword(keywords::Existential) &&
5101 self.look_ahead(1, |t| t.is_keyword(keywords::Type))
5104 fn is_auto_trait_item(&mut self) -> bool {
5106 (self.token.is_keyword(keywords::Auto)
5107 && self.look_ahead(1, |t| t.is_keyword(keywords::Trait)))
5108 || // unsafe auto trait
5109 (self.token.is_keyword(keywords::Unsafe) &&
5110 self.look_ahead(1, |t| t.is_keyword(keywords::Auto)) &&
5111 self.look_ahead(2, |t| t.is_keyword(keywords::Trait)))
5114 fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility, lo: Span)
5115 -> PResult<'a, Option<P<Item>>> {
5116 let token_lo = self.span;
5117 let (ident, def) = match self.token {
5118 token::Ident(ident, false) if ident.name == keywords::Macro.name() => {
5120 let ident = self.parse_ident()?;
5121 let tokens = if self.check(&token::OpenDelim(token::Brace)) {
5122 match self.parse_token_tree() {
5123 TokenTree::Delimited(_, _, tts) => tts,
5124 _ => unreachable!(),
5126 } else if self.check(&token::OpenDelim(token::Paren)) {
5127 let args = self.parse_token_tree();
5128 let body = if self.check(&token::OpenDelim(token::Brace)) {
5129 self.parse_token_tree()
5134 TokenStream::new(vec![
5136 TokenTree::Token(token_lo.to(self.prev_span), token::FatArrow).into(),
5144 (ident, ast::MacroDef { tokens: tokens.into(), legacy: false })
5146 token::Ident(ident, _) if ident.name == "macro_rules" &&
5147 self.look_ahead(1, |t| *t == token::Not) => {
5148 let prev_span = self.prev_span;
5149 self.complain_if_pub_macro(&vis.node, prev_span);
5153 let ident = self.parse_ident()?;
5154 let (delim, tokens) = self.expect_delimited_token_tree()?;
5155 if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
5156 self.report_invalid_macro_expansion_item();
5159 (ident, ast::MacroDef { tokens: tokens, legacy: true })
5161 _ => return Ok(None),
5164 let span = lo.to(self.prev_span);
5165 Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
5168 fn parse_stmt_without_recovery(&mut self,
5169 macro_legacy_warnings: bool)
5170 -> PResult<'a, Option<Stmt>> {
5171 maybe_whole!(self, NtStmt, |x| Some(x));
5173 let attrs = self.parse_outer_attributes()?;
5176 Ok(Some(if self.eat_keyword(keywords::Let) {
5178 id: ast::DUMMY_NODE_ID,
5179 node: StmtKind::Local(self.parse_local(attrs.into())?),
5180 span: lo.to(self.prev_span),
5182 } else if let Some(macro_def) = self.eat_macro_def(
5184 &source_map::respan(lo, VisibilityKind::Inherited),
5188 id: ast::DUMMY_NODE_ID,
5189 node: StmtKind::Item(macro_def),
5190 span: lo.to(self.prev_span),
5192 // Starts like a simple path, being careful to avoid contextual keywords
5193 // such as a union items, item with `crate` visibility or auto trait items.
5194 // Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
5195 // like a path (1 token), but it fact not a path.
5196 // `union::b::c` - path, `union U { ... }` - not a path.
5197 // `crate::b::c` - path, `crate struct S;` - not a path.
5198 } else if self.token.is_path_start() &&
5199 !self.token.is_qpath_start() &&
5200 !self.is_union_item() &&
5201 !self.is_crate_vis() &&
5202 !self.is_existential_type_decl() &&
5203 !self.is_auto_trait_item() &&
5204 !self.is_async_fn() {
5205 let pth = self.parse_path(PathStyle::Expr)?;
5207 if !self.eat(&token::Not) {
5208 let expr = if self.check(&token::OpenDelim(token::Brace)) {
5209 self.parse_struct_expr(lo, pth, ThinVec::new())?
5211 let hi = self.prev_span;
5212 self.mk_expr(lo.to(hi), ExprKind::Path(None, pth), ThinVec::new())
5215 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
5216 let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
5217 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
5220 return Ok(Some(Stmt {
5221 id: ast::DUMMY_NODE_ID,
5222 node: StmtKind::Expr(expr),
5223 span: lo.to(self.prev_span),
5227 // it's a macro invocation
5228 let id = match self.token {
5229 token::OpenDelim(_) => keywords::Invalid.ident(), // no special identifier
5230 _ => self.parse_ident()?,
5233 // check that we're pointing at delimiters (need to check
5234 // again after the `if`, because of `parse_ident`
5235 // consuming more tokens).
5237 token::OpenDelim(_) => {}
5239 // we only expect an ident if we didn't parse one
5241 let ident_str = if id.name == keywords::Invalid.name() {
5246 let tok_str = self.this_token_descr();
5247 let mut err = self.fatal(&format!("expected {}`(` or `{{`, found {}",
5250 err.span_label(self.span, format!("expected {}`(` or `{{`", ident_str));
5255 let (delim, tts) = self.expect_delimited_token_tree()?;
5256 let hi = self.prev_span;
5258 let style = if delim == MacDelimiter::Brace {
5259 MacStmtStyle::Braces
5261 MacStmtStyle::NoBraces
5264 if id.name == keywords::Invalid.name() {
5265 let mac = respan(lo.to(hi), Mac_ { path: pth, tts, delim });
5266 let node = if delim == MacDelimiter::Brace ||
5267 self.token == token::Semi || self.token == token::Eof {
5268 StmtKind::Mac(P((mac, style, attrs.into())))
5270 // We used to incorrectly stop parsing macro-expanded statements here.
5271 // If the next token will be an error anyway but could have parsed with the
5272 // earlier behavior, stop parsing here and emit a warning to avoid breakage.
5273 else if macro_legacy_warnings && self.token.can_begin_expr() && match self.token {
5274 // These can continue an expression, so we can't stop parsing and warn.
5275 token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
5276 token::BinOp(token::Minus) | token::BinOp(token::Star) |
5277 token::BinOp(token::And) | token::BinOp(token::Or) |
5278 token::AndAnd | token::OrOr |
5279 token::DotDot | token::DotDotDot | token::DotDotEq => false,
5282 self.warn_missing_semicolon();
5283 StmtKind::Mac(P((mac, style, attrs.into())))
5285 let e = self.mk_expr(mac.span, ExprKind::Mac(mac), ThinVec::new());
5286 let e = self.maybe_recover_from_bad_qpath(e, true)?;
5287 let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
5288 let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
5292 id: ast::DUMMY_NODE_ID,
5297 // if it has a special ident, it's definitely an item
5299 // Require a semicolon or braces.
5300 if style != MacStmtStyle::Braces && !self.eat(&token::Semi) {
5301 self.report_invalid_macro_expansion_item();
5303 let span = lo.to(hi);
5305 id: ast::DUMMY_NODE_ID,
5307 node: StmtKind::Item({
5309 span, id /*id is good here*/,
5310 ItemKind::Mac(respan(span, Mac_ { path: pth, tts, delim })),
5311 respan(lo, VisibilityKind::Inherited),
5317 // FIXME: Bad copy of attrs
5318 let old_directory_ownership =
5319 mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
5320 let item = self.parse_item_(attrs.clone(), false, true)?;
5321 self.directory.ownership = old_directory_ownership;
5325 id: ast::DUMMY_NODE_ID,
5326 span: lo.to(i.span),
5327 node: StmtKind::Item(i),
5330 let unused_attrs = |attrs: &[Attribute], s: &mut Self| {
5331 if !attrs.is_empty() {
5332 if s.prev_token_kind == PrevTokenKind::DocComment {
5333 s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
5334 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
5335 s.span_err(s.span, "expected statement after outer attribute");
5340 // Do not attempt to parse an expression if we're done here.
5341 if self.token == token::Semi {
5342 unused_attrs(&attrs, self);
5347 if self.token == token::CloseDelim(token::Brace) {
5348 unused_attrs(&attrs, self);
5352 // Remainder are line-expr stmts.
5353 let e = self.parse_expr_res(
5354 Restrictions::STMT_EXPR, Some(attrs.into()))?;
5356 id: ast::DUMMY_NODE_ID,
5357 span: lo.to(e.span),
5358 node: StmtKind::Expr(e),
5365 /// Checks if this expression is a successfully parsed statement.
5366 fn expr_is_complete(&mut self, e: &Expr) -> bool {
5367 self.restrictions.contains(Restrictions::STMT_EXPR) &&
5368 !classify::expr_requires_semi_to_be_stmt(e)
5371 /// Parses a block. No inner attributes are allowed.
5372 pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
5373 maybe_whole!(self, NtBlock, |x| x);
5377 if !self.eat(&token::OpenDelim(token::Brace)) {
5379 let tok = self.this_token_descr();
5380 let mut e = self.span_fatal(sp, &format!("expected `{{`, found {}", tok));
5381 let do_not_suggest_help =
5382 self.token.is_keyword(keywords::In) || self.token == token::Colon;
5384 if self.token.is_ident_named("and") {
5385 e.span_suggestion_short(
5387 "use `&&` instead of `and` for the boolean operator",
5389 Applicability::MaybeIncorrect,
5392 if self.token.is_ident_named("or") {
5393 e.span_suggestion_short(
5395 "use `||` instead of `or` for the boolean operator",
5397 Applicability::MaybeIncorrect,
5401 // Check to see if the user has written something like
5406 // Which is valid in other languages, but not Rust.
5407 match self.parse_stmt_without_recovery(false) {
5409 if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
5410 || do_not_suggest_help {
5411 // if the next token is an open brace (e.g., `if a b {`), the place-
5412 // inside-a-block suggestion would be more likely wrong than right
5413 e.span_label(sp, "expected `{`");
5416 let mut stmt_span = stmt.span;
5417 // expand the span to include the semicolon, if it exists
5418 if self.eat(&token::Semi) {
5419 stmt_span = stmt_span.with_hi(self.prev_span.hi());
5421 let sugg = pprust::to_string(|s| {
5422 use crate::print::pprust::{PrintState, INDENT_UNIT};
5423 s.ibox(INDENT_UNIT)?;
5425 s.print_stmt(&stmt)?;
5426 s.bclose_maybe_open(stmt.span, INDENT_UNIT, false)
5430 "try placing this code inside a block",
5432 // speculative, has been misleading in the past (closed Issue #46836)
5433 Applicability::MaybeIncorrect
5437 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
5438 self.cancel(&mut e);
5442 e.span_label(sp, "expected `{`");
5446 self.parse_block_tail(lo, BlockCheckMode::Default)
5449 /// Parses a block. Inner attributes are allowed.
5450 fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
5451 maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
5454 self.expect(&token::OpenDelim(token::Brace))?;
5455 Ok((self.parse_inner_attributes()?,
5456 self.parse_block_tail(lo, BlockCheckMode::Default)?))
5459 /// Parses the rest of a block expression or function body.
5460 /// Precondition: already parsed the '{'.
5461 fn parse_block_tail(&mut self, lo: Span, s: BlockCheckMode) -> PResult<'a, P<Block>> {
5462 let mut stmts = vec![];
5463 while !self.eat(&token::CloseDelim(token::Brace)) {
5464 let stmt = match self.parse_full_stmt(false) {
5467 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
5469 id: ast::DUMMY_NODE_ID,
5470 node: StmtKind::Expr(DummyResult::raw_expr(self.span, true)),
5476 if let Some(stmt) = stmt {
5478 } else if self.token == token::Eof {
5481 // Found only `;` or `}`.
5487 id: ast::DUMMY_NODE_ID,
5489 span: lo.to(self.prev_span),
5493 /// Parses a statement, including the trailing semicolon.
5494 crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
5495 // skip looking for a trailing semicolon when we have an interpolated statement
5496 maybe_whole!(self, NtStmt, |x| Some(x));
5498 let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
5500 None => return Ok(None),
5504 StmtKind::Expr(ref expr) if self.token != token::Eof => {
5505 // expression without semicolon
5506 if classify::expr_requires_semi_to_be_stmt(expr) {
5507 // Just check for errors and recover; do not eat semicolon yet.
5509 self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
5512 self.recover_stmt();
5516 StmtKind::Local(..) => {
5517 // We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
5518 if macro_legacy_warnings && self.token != token::Semi {
5519 self.warn_missing_semicolon();
5521 self.expect_one_of(&[], &[token::Semi])?;
5527 if self.eat(&token::Semi) {
5528 stmt = stmt.add_trailing_semicolon();
5531 stmt.span = stmt.span.with_hi(self.prev_span.hi());
5535 fn warn_missing_semicolon(&self) {
5536 self.diagnostic().struct_span_warn(self.span, {
5537 &format!("expected `;`, found {}", self.this_token_descr())
5539 "This was erroneously allowed and will become a hard error in a future release"
5543 fn err_dotdotdot_syntax(&self, span: Span) {
5544 self.diagnostic().struct_span_err(span, {
5545 "unexpected token: `...`"
5547 span, "use `..` for an exclusive range", "..".to_owned(),
5548 Applicability::MaybeIncorrect
5550 span, "or `..=` for an inclusive range", "..=".to_owned(),
5551 Applicability::MaybeIncorrect
5555 /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
5558 /// BOUND = TY_BOUND | LT_BOUND
5559 /// LT_BOUND = LIFETIME (e.g., `'a`)
5560 /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
5561 /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
5563 fn parse_generic_bounds_common(&mut self,
5565 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
5566 let mut bounds = Vec::new();
5567 let mut negative_bounds = Vec::new();
5568 let mut last_plus_span = None;
5569 let mut was_negative = false;
5571 // This needs to be synchronized with `Token::can_begin_bound`.
5572 let is_bound_start = self.check_path() || self.check_lifetime() ||
5573 self.check(&token::Not) || // used for error reporting only
5574 self.check(&token::Question) ||
5575 self.check_keyword(keywords::For) ||
5576 self.check(&token::OpenDelim(token::Paren));
5579 let has_parens = self.eat(&token::OpenDelim(token::Paren));
5580 let inner_lo = self.span;
5581 let is_negative = self.eat(&token::Not);
5582 let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
5583 if self.token.is_lifetime() {
5584 if let Some(question_span) = question {
5585 self.span_err(question_span,
5586 "`?` may only modify trait bounds, not lifetime bounds");
5588 bounds.push(GenericBound::Outlives(self.expect_lifetime()));
5590 let inner_span = inner_lo.to(self.prev_span);
5591 self.expect(&token::CloseDelim(token::Paren))?;
5592 let mut err = self.struct_span_err(
5593 lo.to(self.prev_span),
5594 "parenthesized lifetime bounds are not supported"
5596 if let Ok(snippet) = self.sess.source_map().span_to_snippet(inner_span) {
5597 err.span_suggestion_short(
5598 lo.to(self.prev_span),
5599 "remove the parentheses",
5601 Applicability::MachineApplicable
5607 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
5608 let path = self.parse_path(PathStyle::Type)?;
5610 self.expect(&token::CloseDelim(token::Paren))?;
5612 let poly_span = lo.to(self.prev_span);
5614 was_negative = true;
5615 if let Some(sp) = last_plus_span.or(colon_span) {
5616 negative_bounds.push(sp.to(poly_span));
5619 let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span);
5620 let modifier = if question.is_some() {
5621 TraitBoundModifier::Maybe
5623 TraitBoundModifier::None
5625 bounds.push(GenericBound::Trait(poly_trait, modifier));
5632 if !allow_plus || !self.eat_plus() {
5635 last_plus_span = Some(self.prev_span);
5639 if !negative_bounds.is_empty() || was_negative {
5640 let plural = negative_bounds.len() > 1;
5641 let last_span = negative_bounds.last().map(|sp| *sp);
5642 let mut err = self.struct_span_err(
5644 "negative trait bounds are not supported",
5646 if let Some(sp) = last_span {
5647 err.span_label(sp, "negative trait bounds are not supported");
5649 if let Some(bound_list) = colon_span {
5650 let bound_list = bound_list.to(self.prev_span);
5651 let mut new_bound_list = String::new();
5652 if !bounds.is_empty() {
5653 let mut snippets = bounds.iter().map(|bound| bound.span())
5654 .map(|span| self.sess.source_map().span_to_snippet(span));
5655 while let Some(Ok(snippet)) = snippets.next() {
5656 new_bound_list.push_str(" + ");
5657 new_bound_list.push_str(&snippet);
5659 new_bound_list = new_bound_list.replacen(" +", ":", 1);
5661 err.span_suggestion_hidden(
5663 &format!("remove the trait bound{}", if plural { "s" } else { "" }),
5665 Applicability::MachineApplicable,
5674 fn parse_generic_bounds(&mut self, colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
5675 self.parse_generic_bounds_common(true, colon_span)
5678 /// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
5681 /// BOUND = LT_BOUND (e.g., `'a`)
5683 fn parse_lt_param_bounds(&mut self) -> GenericBounds {
5684 let mut lifetimes = Vec::new();
5685 while self.check_lifetime() {
5686 lifetimes.push(ast::GenericBound::Outlives(self.expect_lifetime()));
5688 if !self.eat_plus() {
5695 /// Matches `typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?`.
5696 fn parse_ty_param(&mut self,
5697 preceding_attrs: Vec<Attribute>)
5698 -> PResult<'a, GenericParam> {
5699 let ident = self.parse_ident()?;
5701 // Parse optional colon and param bounds.
5702 let bounds = if self.eat(&token::Colon) {
5703 self.parse_generic_bounds(Some(self.prev_span))?
5708 let default = if self.eat(&token::Eq) {
5709 Some(self.parse_ty()?)
5716 id: ast::DUMMY_NODE_ID,
5717 attrs: preceding_attrs.into(),
5719 kind: GenericParamKind::Type {
5725 /// Parses the following grammar:
5727 /// TraitItemAssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
5728 fn parse_trait_item_assoc_ty(&mut self)
5729 -> PResult<'a, (Ident, TraitItemKind, ast::Generics)> {
5730 let ident = self.parse_ident()?;
5731 let mut generics = self.parse_generics()?;
5733 // Parse optional colon and param bounds.
5734 let bounds = if self.eat(&token::Colon) {
5735 self.parse_generic_bounds(None)?
5739 generics.where_clause = self.parse_where_clause()?;
5741 let default = if self.eat(&token::Eq) {
5742 Some(self.parse_ty()?)
5746 self.expect(&token::Semi)?;
5748 Ok((ident, TraitItemKind::Type(bounds, default), generics))
5751 fn parse_const_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> {
5752 self.expect_keyword(keywords::Const)?;
5753 let ident = self.parse_ident()?;
5754 self.expect(&token::Colon)?;
5755 let ty = self.parse_ty()?;
5759 id: ast::DUMMY_NODE_ID,
5760 attrs: preceding_attrs.into(),
5762 kind: GenericParamKind::Const {
5768 /// Parses a (possibly empty) list of lifetime and type parameters, possibly including
5769 /// a trailing comma and erroneous trailing attributes.
5770 crate fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
5771 let mut params = Vec::new();
5773 let attrs = self.parse_outer_attributes()?;
5774 if self.check_lifetime() {
5775 let lifetime = self.expect_lifetime();
5776 // Parse lifetime parameter.
5777 let bounds = if self.eat(&token::Colon) {
5778 self.parse_lt_param_bounds()
5782 params.push(ast::GenericParam {
5783 ident: lifetime.ident,
5785 attrs: attrs.into(),
5787 kind: ast::GenericParamKind::Lifetime,
5789 } else if self.check_keyword(keywords::Const) {
5790 // Parse const parameter.
5791 params.push(self.parse_const_param(attrs)?);
5792 } else if self.check_ident() {
5793 // Parse type parameter.
5794 params.push(self.parse_ty_param(attrs)?);
5796 // Check for trailing attributes and stop parsing.
5797 if !attrs.is_empty() {
5798 if !params.is_empty() {
5799 self.struct_span_err(
5801 &format!("trailing attribute after generic parameter"),
5803 .span_label(attrs[0].span, "attributes must go before parameters")
5806 self.struct_span_err(
5808 &format!("attribute without generic parameters"),
5812 "attributes are only permitted when preceding parameters",
5820 if !self.eat(&token::Comma) {
5827 /// Parses a set of optional generic type parameter declarations. Where
5828 /// clauses are not parsed here, and must be added later via
5829 /// `parse_where_clause()`.
5831 /// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
5832 /// | ( < lifetimes , typaramseq ( , )? > )
5833 /// where typaramseq = ( typaram ) | ( typaram , typaramseq )
5834 fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
5835 maybe_whole!(self, NtGenerics, |x| x);
5837 let span_lo = self.span;
5839 let params = self.parse_generic_params()?;
5843 where_clause: WhereClause {
5844 id: ast::DUMMY_NODE_ID,
5845 predicates: Vec::new(),
5846 span: syntax_pos::DUMMY_SP,
5848 span: span_lo.to(self.prev_span),
5851 Ok(ast::Generics::default())
5855 /// Parses generic args (within a path segment) with recovery for extra leading angle brackets.
5856 /// For the purposes of understanding the parsing logic of generic arguments, this function
5857 /// can be thought of being the same as just calling `self.parse_generic_args()` if the source
5858 /// had the correct amount of leading angle brackets.
5860 /// ```ignore (diagnostics)
5861 /// bar::<<<<T as Foo>::Output>();
5862 /// ^^ help: remove extra angle brackets
5864 fn parse_generic_args_with_leaning_angle_bracket_recovery(
5868 ) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
5869 // We need to detect whether there are extra leading left angle brackets and produce an
5870 // appropriate error and suggestion. This cannot be implemented by looking ahead at
5871 // upcoming tokens for a matching `>` character - if there are unmatched `<` tokens
5872 // then there won't be matching `>` tokens to find.
5874 // To explain how this detection works, consider the following example:
5876 // ```ignore (diagnostics)
5877 // bar::<<<<T as Foo>::Output>();
5878 // ^^ help: remove extra angle brackets
5881 // Parsing of the left angle brackets starts in this function. We start by parsing the
5882 // `<` token (incrementing the counter of unmatched angle brackets on `Parser` via
5885 // *Upcoming tokens:* `<<<<T as Foo>::Output>;`
5886 // *Unmatched count:* 1
5887 // *`parse_path_segment` calls deep:* 0
5889 // This has the effect of recursing as this function is called if a `<` character
5890 // is found within the expected generic arguments:
5892 // *Upcoming tokens:* `<<<T as Foo>::Output>;`
5893 // *Unmatched count:* 2
5894 // *`parse_path_segment` calls deep:* 1
5896 // Eventually we will have recursed until having consumed all of the `<` tokens and
5897 // this will be reflected in the count:
5899 // *Upcoming tokens:* `T as Foo>::Output>;`
5900 // *Unmatched count:* 4
5901 // `parse_path_segment` calls deep:* 3
5903 // The parser will continue until reaching the first `>` - this will decrement the
5904 // unmatched angle bracket count and return to the parent invocation of this function
5905 // having succeeded in parsing:
5907 // *Upcoming tokens:* `::Output>;`
5908 // *Unmatched count:* 3
5909 // *`parse_path_segment` calls deep:* 2
5911 // This will continue until the next `>` character which will also return successfully
5912 // to the parent invocation of this function and decrement the count:
5914 // *Upcoming tokens:* `;`
5915 // *Unmatched count:* 2
5916 // *`parse_path_segment` calls deep:* 1
5918 // At this point, this function will expect to find another matching `>` character but
5919 // won't be able to and will return an error. This will continue all the way up the
5920 // call stack until the first invocation:
5922 // *Upcoming tokens:* `;`
5923 // *Unmatched count:* 2
5924 // *`parse_path_segment` calls deep:* 0
5926 // In doing this, we have managed to work out how many unmatched leading left angle
5927 // brackets there are, but we cannot recover as the unmatched angle brackets have
5928 // already been consumed. To remedy this, we keep a snapshot of the parser state
5929 // before we do the above. We can then inspect whether we ended up with a parsing error
5930 // and unmatched left angle brackets and if so, restore the parser state before we
5931 // consumed any `<` characters to emit an error and consume the erroneous tokens to
5932 // recover by attempting to parse again.
5934 // In practice, the recursion of this function is indirect and there will be other
5935 // locations that consume some `<` characters - as long as we update the count when
5936 // this happens, it isn't an issue.
5938 let is_first_invocation = style == PathStyle::Expr;
5939 // Take a snapshot before attempting to parse - we can restore this later.
5940 let snapshot = if is_first_invocation {
5946 debug!("parse_generic_args_with_leading_angle_bracket_recovery: (snapshotting)");
5947 match self.parse_generic_args() {
5948 Ok(value) => Ok(value),
5949 Err(ref mut e) if is_first_invocation && self.unmatched_angle_bracket_count > 0 => {
5950 // Cancel error from being unable to find `>`. We know the error
5951 // must have been this due to a non-zero unmatched angle bracket
5955 // Swap `self` with our backup of the parser state before attempting to parse
5956 // generic arguments.
5957 let snapshot = mem::replace(self, snapshot.unwrap());
5960 "parse_generic_args_with_leading_angle_bracket_recovery: (snapshot failure) \
5961 snapshot.count={:?}",
5962 snapshot.unmatched_angle_bracket_count,
5965 // Eat the unmatched angle brackets.
5966 for _ in 0..snapshot.unmatched_angle_bracket_count {
5970 // Make a span over ${unmatched angle bracket count} characters.
5971 let span = lo.with_hi(
5972 lo.lo() + BytePos(snapshot.unmatched_angle_bracket_count)
5974 let plural = snapshot.unmatched_angle_bracket_count > 1;
5979 "unmatched angle bracket{}",
5980 if plural { "s" } else { "" }
5986 "remove extra angle bracket{}",
5987 if plural { "s" } else { "" }
5990 Applicability::MachineApplicable,
5994 // Try again without unmatched angle bracket characters.
5995 self.parse_generic_args()
6001 /// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
6002 /// possibly including trailing comma.
6003 fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
6004 let mut args = Vec::new();
6005 let mut bindings = Vec::new();
6006 let mut misplaced_assoc_ty_bindings: Vec<Span> = Vec::new();
6007 let mut assoc_ty_bindings: Vec<Span> = Vec::new();
6009 let args_lo = self.span;
6012 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
6013 // Parse lifetime argument.
6014 args.push(GenericArg::Lifetime(self.expect_lifetime()));
6015 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
6016 } else if self.check_ident() && self.look_ahead(1, |t| t == &token::Eq) {
6017 // Parse associated type binding.
6019 let ident = self.parse_ident()?;
6021 let ty = self.parse_ty()?;
6022 let span = lo.to(self.prev_span);
6023 bindings.push(TypeBinding {
6024 id: ast::DUMMY_NODE_ID,
6029 assoc_ty_bindings.push(span);
6030 } else if self.check_const_arg() {
6031 // FIXME(const_generics): to distinguish between idents for types and consts,
6032 // we should introduce a GenericArg::Ident in the AST and distinguish when
6033 // lowering to the HIR. For now, idents for const args are not permitted.
6035 // Parse const argument.
6036 let expr = if let token::OpenDelim(token::Brace) = self.token {
6037 self.parse_block_expr(None, self.span, BlockCheckMode::Default, ThinVec::new())?
6038 } else if self.token.is_ident() {
6039 // FIXME(const_generics): to distinguish between idents for types and consts,
6040 // we should introduce a GenericArg::Ident in the AST and distinguish when
6041 // lowering to the HIR. For now, idents for const args are not permitted.
6043 self.fatal("identifiers may currently not be used for const generics")
6046 // FIXME(const_generics): this currently conflicts with emplacement syntax
6047 // with negative integer literals.
6048 self.parse_literal_maybe_minus()?
6050 let value = AnonConst {
6051 id: ast::DUMMY_NODE_ID,
6054 args.push(GenericArg::Const(value));
6055 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
6056 } else if self.check_type() {
6057 // Parse type argument.
6058 args.push(GenericArg::Type(self.parse_ty()?));
6059 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
6064 if !self.eat(&token::Comma) {
6069 // FIXME: we would like to report this in ast_validation instead, but we currently do not
6070 // preserve ordering of generic parameters with respect to associated type binding, so we
6071 // lose that information after parsing.
6072 if misplaced_assoc_ty_bindings.len() > 0 {
6073 let mut err = self.struct_span_err(
6074 args_lo.to(self.prev_span),
6075 "associated type bindings must be declared after generic parameters",
6077 for span in misplaced_assoc_ty_bindings {
6080 "this associated type binding should be moved after the generic parameters",
6086 Ok((args, bindings))
6089 /// Parses an optional where-clause and places it in `generics`.
6091 /// ```ignore (only-for-syntax-highlight)
6092 /// where T : Trait<U, V> + 'b, 'a : 'b
6094 fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
6095 maybe_whole!(self, NtWhereClause, |x| x);
6097 let mut where_clause = WhereClause {
6098 id: ast::DUMMY_NODE_ID,
6099 predicates: Vec::new(),
6100 span: syntax_pos::DUMMY_SP,
6103 if !self.eat_keyword(keywords::Where) {
6104 return Ok(where_clause);
6106 let lo = self.prev_span;
6108 // We are considering adding generics to the `where` keyword as an alternative higher-rank
6109 // parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
6110 // change we parse those generics now, but report an error.
6111 if self.choose_generics_over_qpath() {
6112 let generics = self.parse_generics()?;
6113 self.struct_span_err(
6115 "generic parameters on `where` clauses are reserved for future use",
6117 .span_label(generics.span, "currently unsupported")
6123 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
6124 let lifetime = self.expect_lifetime();
6125 // Bounds starting with a colon are mandatory, but possibly empty.
6126 self.expect(&token::Colon)?;
6127 let bounds = self.parse_lt_param_bounds();
6128 where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
6129 ast::WhereRegionPredicate {
6130 span: lo.to(self.prev_span),
6135 } else if self.check_type() {
6136 // Parse optional `for<'a, 'b>`.
6137 // This `for` is parsed greedily and applies to the whole predicate,
6138 // the bounded type can have its own `for` applying only to it.
6139 // Example 1: for<'a> Trait1<'a>: Trait2<'a /*ok*/>
6140 // Example 2: (for<'a> Trait1<'a>): Trait2<'a /*not ok*/>
6141 // Example 3: for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /*ok*/, 'b /*not ok*/>
6142 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
6144 // Parse type with mandatory colon and (possibly empty) bounds,
6145 // or with mandatory equality sign and the second type.
6146 let ty = self.parse_ty()?;
6147 if self.eat(&token::Colon) {
6148 let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
6149 where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
6150 ast::WhereBoundPredicate {
6151 span: lo.to(self.prev_span),
6152 bound_generic_params: lifetime_defs,
6157 // FIXME: Decide what should be used here, `=` or `==`.
6158 // FIXME: We are just dropping the binders in lifetime_defs on the floor here.
6159 } else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
6160 let rhs_ty = self.parse_ty()?;
6161 where_clause.predicates.push(ast::WherePredicate::EqPredicate(
6162 ast::WhereEqPredicate {
6163 span: lo.to(self.prev_span),
6166 id: ast::DUMMY_NODE_ID,
6170 return self.unexpected();
6176 if !self.eat(&token::Comma) {
6181 where_clause.span = lo.to(self.prev_span);
6185 fn parse_fn_args(&mut self, named_args: bool, allow_c_variadic: bool)
6186 -> PResult<'a, (Vec<Arg> , bool)> {
6187 self.expect(&token::OpenDelim(token::Paren))?;
6190 let mut c_variadic = false;
6191 let (args, recovered): (Vec<Option<Arg>>, bool) =
6192 self.parse_seq_to_before_end(
6193 &token::CloseDelim(token::Paren),
6194 SeqSep::trailing_allowed(token::Comma),
6196 // If the argument is a C-variadic argument we should not
6197 // enforce named arguments.
6198 let enforce_named_args = if p.token == token::DotDotDot {
6203 match p.parse_arg_general(enforce_named_args, false,
6206 if let TyKind::CVarArgs = arg.ty.node {
6208 if p.token != token::CloseDelim(token::Paren) {
6211 "`...` must be the last argument of a C-variadic function");
6222 let lo = p.prev_span;
6223 // Skip every token until next possible arg or end.
6224 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
6225 // Create a placeholder argument for proper arg count (issue #34264).
6226 let span = lo.to(p.prev_span);
6227 Ok(Some(dummy_arg(span)))
6234 self.eat(&token::CloseDelim(token::Paren));
6237 let args: Vec<_> = args.into_iter().filter_map(|x| x).collect();
6239 if c_variadic && args.is_empty() {
6241 "C-variadic function must be declared with at least one named argument");
6244 Ok((args, c_variadic))
6247 /// Parses the argument list and result type of a function declaration.
6248 fn parse_fn_decl(&mut self, allow_c_variadic: bool) -> PResult<'a, P<FnDecl>> {
6250 let (args, c_variadic) = self.parse_fn_args(true, allow_c_variadic)?;
6251 let ret_ty = self.parse_ret_ty(true)?;
6260 /// Returns the parsed optional self argument and whether a self shortcut was used.
6261 fn parse_self_arg(&mut self) -> PResult<'a, Option<Arg>> {
6262 let expect_ident = |this: &mut Self| match this.token {
6263 // Preserve hygienic context.
6264 token::Ident(ident, _) =>
6265 { let span = this.span; this.bump(); Ident::new(ident.name, span) }
6268 let isolated_self = |this: &mut Self, n| {
6269 this.look_ahead(n, |t| t.is_keyword(keywords::SelfLower)) &&
6270 this.look_ahead(n + 1, |t| t != &token::ModSep)
6273 // Parse optional self parameter of a method.
6274 // Only a limited set of initial token sequences is considered self parameters, anything
6275 // else is parsed as a normal function parameter list, so some lookahead is required.
6276 let eself_lo = self.span;
6277 let (eself, eself_ident, eself_hi) = match self.token {
6278 token::BinOp(token::And) => {
6284 (if isolated_self(self, 1) {
6286 SelfKind::Region(None, Mutability::Immutable)
6287 } else if self.look_ahead(1, |t| t.is_keyword(keywords::Mut)) &&
6288 isolated_self(self, 2) {
6291 SelfKind::Region(None, Mutability::Mutable)
6292 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
6293 isolated_self(self, 2) {
6295 let lt = self.expect_lifetime();
6296 SelfKind::Region(Some(lt), Mutability::Immutable)
6297 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
6298 self.look_ahead(2, |t| t.is_keyword(keywords::Mut)) &&
6299 isolated_self(self, 3) {
6301 let lt = self.expect_lifetime();
6303 SelfKind::Region(Some(lt), Mutability::Mutable)
6306 }, expect_ident(self), self.prev_span)
6308 token::BinOp(token::Star) => {
6313 // Emit special error for `self` cases.
6314 let msg = "cannot pass `self` by raw pointer";
6315 (if isolated_self(self, 1) {
6317 self.struct_span_err(self.span, msg)
6318 .span_label(self.span, msg)
6320 SelfKind::Value(Mutability::Immutable)
6321 } else if self.look_ahead(1, |t| t.is_mutability()) &&
6322 isolated_self(self, 2) {
6325 self.struct_span_err(self.span, msg)
6326 .span_label(self.span, msg)
6328 SelfKind::Value(Mutability::Immutable)
6331 }, expect_ident(self), self.prev_span)
6333 token::Ident(..) => {
6334 if isolated_self(self, 0) {
6337 let eself_ident = expect_ident(self);
6338 let eself_hi = self.prev_span;
6339 (if self.eat(&token::Colon) {
6340 let ty = self.parse_ty()?;
6341 SelfKind::Explicit(ty, Mutability::Immutable)
6343 SelfKind::Value(Mutability::Immutable)
6344 }, eself_ident, eself_hi)
6345 } else if self.token.is_keyword(keywords::Mut) &&
6346 isolated_self(self, 1) {
6350 let eself_ident = expect_ident(self);
6351 let eself_hi = self.prev_span;
6352 (if self.eat(&token::Colon) {
6353 let ty = self.parse_ty()?;
6354 SelfKind::Explicit(ty, Mutability::Mutable)
6356 SelfKind::Value(Mutability::Mutable)
6357 }, eself_ident, eself_hi)
6362 _ => return Ok(None),
6365 let eself = source_map::respan(eself_lo.to(eself_hi), eself);
6366 Ok(Some(Arg::from_self(eself, eself_ident)))
6369 /// Parses the parameter list and result type of a function that may have a `self` parameter.
6370 fn parse_fn_decl_with_self<F>(&mut self, parse_arg_fn: F) -> PResult<'a, P<FnDecl>>
6371 where F: FnMut(&mut Parser<'a>) -> PResult<'a, Arg>,
6373 self.expect(&token::OpenDelim(token::Paren))?;
6375 // Parse optional self argument
6376 let self_arg = self.parse_self_arg()?;
6378 // Parse the rest of the function parameter list.
6379 let sep = SeqSep::trailing_allowed(token::Comma);
6380 let (fn_inputs, recovered) = if let Some(self_arg) = self_arg {
6381 if self.check(&token::CloseDelim(token::Paren)) {
6382 (vec![self_arg], false)
6383 } else if self.eat(&token::Comma) {
6384 let mut fn_inputs = vec![self_arg];
6385 let (mut input, recovered) = self.parse_seq_to_before_end(
6386 &token::CloseDelim(token::Paren), sep, parse_arg_fn)?;
6387 fn_inputs.append(&mut input);
6388 (fn_inputs, recovered)
6390 match self.expect_one_of(&[], &[]) {
6391 Err(err) => return Err(err),
6392 Ok(recovered) => (vec![self_arg], recovered),
6396 self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)?
6400 // Parse closing paren and return type.
6401 self.expect(&token::CloseDelim(token::Paren))?;
6405 output: self.parse_ret_ty(true)?,
6410 /// Parses the `|arg, arg|` header of a closure.
6411 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
6412 let inputs_captures = {
6413 if self.eat(&token::OrOr) {
6416 self.expect(&token::BinOp(token::Or))?;
6417 let args = self.parse_seq_to_before_tokens(
6418 &[&token::BinOp(token::Or), &token::OrOr],
6419 SeqSep::trailing_allowed(token::Comma),
6420 TokenExpectType::NoExpect,
6421 |p| p.parse_fn_block_arg()
6427 let output = self.parse_ret_ty(true)?;
6430 inputs: inputs_captures,
6436 /// Parses the name and optional generic types of a function header.
6437 fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> {
6438 let id = self.parse_ident()?;
6439 let generics = self.parse_generics()?;
6443 fn mk_item(&mut self, span: Span, ident: Ident, node: ItemKind, vis: Visibility,
6444 attrs: Vec<Attribute>) -> P<Item> {
6448 id: ast::DUMMY_NODE_ID,
6456 /// Parses an item-position function declaration.
6457 fn parse_item_fn(&mut self,
6459 asyncness: Spanned<IsAsync>,
6460 constness: Spanned<Constness>,
6462 -> PResult<'a, ItemInfo> {
6463 let (ident, mut generics) = self.parse_fn_header()?;
6464 let allow_c_variadic = abi == Abi::C && unsafety == Unsafety::Unsafe;
6465 let decl = self.parse_fn_decl(allow_c_variadic)?;
6466 generics.where_clause = self.parse_where_clause()?;
6467 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
6468 let header = FnHeader { unsafety, asyncness, constness, abi };
6469 Ok((ident, ItemKind::Fn(decl, header, generics, body), Some(inner_attrs)))
6472 /// Returns `true` if we are looking at `const ID`
6473 /// (returns `false` for things like `const fn`, etc.).
6474 fn is_const_item(&mut self) -> bool {
6475 self.token.is_keyword(keywords::Const) &&
6476 !self.look_ahead(1, |t| t.is_keyword(keywords::Fn)) &&
6477 !self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe))
6480 /// Parses all the "front matter" for a `fn` declaration, up to
6481 /// and including the `fn` keyword:
6485 /// - `const unsafe fn`
6488 fn parse_fn_front_matter(&mut self)
6496 let is_const_fn = self.eat_keyword(keywords::Const);
6497 let const_span = self.prev_span;
6498 let unsafety = self.parse_unsafety();
6499 let asyncness = self.parse_asyncness();
6500 let asyncness = respan(self.prev_span, asyncness);
6501 let (constness, unsafety, abi) = if is_const_fn {
6502 (respan(const_span, Constness::Const), unsafety, Abi::Rust)
6504 let abi = if self.eat_keyword(keywords::Extern) {
6505 self.parse_opt_abi()?.unwrap_or(Abi::C)
6509 (respan(self.prev_span, Constness::NotConst), unsafety, abi)
6511 self.expect_keyword(keywords::Fn)?;
6512 Ok((constness, unsafety, asyncness, abi))
6515 /// Parses an impl item.
6516 pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> {
6517 maybe_whole!(self, NtImplItem, |x| x);
6518 let attrs = self.parse_outer_attributes()?;
6519 let mut unclosed_delims = vec![];
6520 let (mut item, tokens) = self.collect_tokens(|this| {
6521 let item = this.parse_impl_item_(at_end, attrs);
6522 unclosed_delims.append(&mut this.unclosed_delims);
6525 self.unclosed_delims.append(&mut unclosed_delims);
6527 // See `parse_item` for why this clause is here.
6528 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
6529 item.tokens = Some(tokens);
6534 fn parse_impl_item_(&mut self,
6536 mut attrs: Vec<Attribute>) -> PResult<'a, ImplItem> {
6538 let vis = self.parse_visibility(false)?;
6539 let defaultness = self.parse_defaultness();
6540 let (name, node, generics) = if let Some(type_) = self.eat_type() {
6541 let (name, alias, generics) = type_?;
6542 let kind = match alias {
6543 AliasKind::Weak(typ) => ast::ImplItemKind::Type(typ),
6544 AliasKind::Existential(bounds) => ast::ImplItemKind::Existential(bounds),
6546 (name, kind, generics)
6547 } else if self.is_const_item() {
6548 // This parses the grammar:
6549 // ImplItemConst = "const" Ident ":" Ty "=" Expr ";"
6550 self.expect_keyword(keywords::Const)?;
6551 let name = self.parse_ident()?;
6552 self.expect(&token::Colon)?;
6553 let typ = self.parse_ty()?;
6554 self.expect(&token::Eq)?;
6555 let expr = self.parse_expr()?;
6556 self.expect(&token::Semi)?;
6557 (name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default())
6559 let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?;
6560 attrs.extend(inner_attrs);
6561 (name, node, generics)
6565 id: ast::DUMMY_NODE_ID,
6566 span: lo.to(self.prev_span),
6577 fn complain_if_pub_macro(&mut self, vis: &VisibilityKind, sp: Span) {
6579 VisibilityKind::Inherited => {}
6581 let is_macro_rules: bool = match self.token {
6582 token::Ident(sid, _) => sid.name == Symbol::intern("macro_rules"),
6585 let mut err = if is_macro_rules {
6586 let mut err = self.diagnostic()
6587 .struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
6588 err.span_suggestion(
6590 "try exporting the macro",
6591 "#[macro_export]".to_owned(),
6592 Applicability::MaybeIncorrect // speculative
6596 let mut err = self.diagnostic()
6597 .struct_span_err(sp, "can't qualify macro invocation with `pub`");
6598 err.help("try adjusting the macro to put `pub` inside the invocation");
6606 fn missing_assoc_item_kind_err(&mut self, item_type: &str, prev_span: Span)
6607 -> DiagnosticBuilder<'a>
6609 let expected_kinds = if item_type == "extern" {
6610 "missing `fn`, `type`, or `static`"
6612 "missing `fn`, `type`, or `const`"
6615 // Given this code `path(`, it seems like this is not
6616 // setting the visibility of a macro invocation, but rather
6617 // a mistyped method declaration.
6618 // Create a diagnostic pointing out that `fn` is missing.
6620 // x | pub path(&self) {
6621 // | ^ missing `fn`, `type`, or `const`
6623 // ^^ `sp` below will point to this
6624 let sp = prev_span.between(self.prev_span);
6625 let mut err = self.diagnostic().struct_span_err(
6627 &format!("{} for {}-item declaration",
6628 expected_kinds, item_type));
6629 err.span_label(sp, expected_kinds);
6633 /// Parse a method or a macro invocation in a trait impl.
6634 fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool)
6635 -> PResult<'a, (Ident, Vec<Attribute>, ast::Generics,
6636 ast::ImplItemKind)> {
6637 // code copied from parse_macro_use_or_failure... abstraction!
6638 if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(vis), at_end)? {
6640 Ok((keywords::Invalid.ident(), vec![], ast::Generics::default(),
6641 ast::ImplItemKind::Macro(mac)))
6643 let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
6644 let ident = self.parse_ident()?;
6645 let mut generics = self.parse_generics()?;
6646 let decl = self.parse_fn_decl_with_self(|p| p.parse_arg())?;
6647 generics.where_clause = self.parse_where_clause()?;
6649 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
6650 let header = ast::FnHeader { abi, unsafety, constness, asyncness };
6651 Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method(
6652 ast::MethodSig { header, decl },
6658 /// Parses `trait Foo { ... }` or `trait Foo = Bar;`.
6659 fn parse_item_trait(&mut self, is_auto: IsAuto, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
6660 let ident = self.parse_ident()?;
6661 let mut tps = self.parse_generics()?;
6663 // Parse optional colon and supertrait bounds.
6664 let bounds = if self.eat(&token::Colon) {
6665 self.parse_generic_bounds(Some(self.prev_span))?
6670 if self.eat(&token::Eq) {
6671 // it's a trait alias
6672 let bounds = self.parse_generic_bounds(None)?;
6673 tps.where_clause = self.parse_where_clause()?;
6674 self.expect(&token::Semi)?;
6675 if is_auto == IsAuto::Yes {
6676 let msg = "trait aliases cannot be `auto`";
6677 self.struct_span_err(self.prev_span, msg)
6678 .span_label(self.prev_span, msg)
6681 if unsafety != Unsafety::Normal {
6682 let msg = "trait aliases cannot be `unsafe`";
6683 self.struct_span_err(self.prev_span, msg)
6684 .span_label(self.prev_span, msg)
6687 Ok((ident, ItemKind::TraitAlias(tps, bounds), None))
6689 // it's a normal trait
6690 tps.where_clause = self.parse_where_clause()?;
6691 self.expect(&token::OpenDelim(token::Brace))?;
6692 let mut trait_items = vec![];
6693 while !self.eat(&token::CloseDelim(token::Brace)) {
6694 let mut at_end = false;
6695 match self.parse_trait_item(&mut at_end) {
6696 Ok(item) => trait_items.push(item),
6700 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
6705 Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None))
6709 fn choose_generics_over_qpath(&self) -> bool {
6710 // There's an ambiguity between generic parameters and qualified paths in impls.
6711 // If we see `<` it may start both, so we have to inspect some following tokens.
6712 // The following combinations can only start generics,
6713 // but not qualified paths (with one exception):
6714 // `<` `>` - empty generic parameters
6715 // `<` `#` - generic parameters with attributes
6716 // `<` (LIFETIME|IDENT) `>` - single generic parameter
6717 // `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
6718 // `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
6719 // `<` (LIFETIME|IDENT) `=` - generic parameter with a default
6720 // `<` const - generic const parameter
6721 // The only truly ambiguous case is
6722 // `<` IDENT `>` `::` IDENT ...
6723 // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
6724 // because this is what almost always expected in practice, qualified paths in impls
6725 // (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
6726 self.token == token::Lt &&
6727 (self.look_ahead(1, |t| t == &token::Pound || t == &token::Gt) ||
6728 self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) &&
6729 self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma ||
6730 t == &token::Colon || t == &token::Eq) ||
6731 self.look_ahead(1, |t| t.is_keyword(keywords::Const)))
6734 fn parse_impl_body(&mut self) -> PResult<'a, (Vec<ImplItem>, Vec<Attribute>)> {
6735 self.expect(&token::OpenDelim(token::Brace))?;
6736 let attrs = self.parse_inner_attributes()?;
6738 let mut impl_items = Vec::new();
6739 while !self.eat(&token::CloseDelim(token::Brace)) {
6740 let mut at_end = false;
6741 match self.parse_impl_item(&mut at_end) {
6742 Ok(impl_item) => impl_items.push(impl_item),
6746 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
6751 Ok((impl_items, attrs))
6754 /// Parses an implementation item, `impl` keyword is already parsed.
6756 /// impl<'a, T> TYPE { /* impl items */ }
6757 /// impl<'a, T> TRAIT for TYPE { /* impl items */ }
6758 /// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
6760 /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
6761 /// `impl` GENERICS `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}`
6762 /// `impl` GENERICS `!`? TYPE (`where` PREDICATES)? `{` BODY `}`
6763 fn parse_item_impl(&mut self, unsafety: Unsafety, defaultness: Defaultness)
6764 -> PResult<'a, ItemInfo> {
6765 // First, parse generic parameters if necessary.
6766 let mut generics = if self.choose_generics_over_qpath() {
6767 self.parse_generics()?
6769 ast::Generics::default()
6772 // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
6773 let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
6775 ast::ImplPolarity::Negative
6777 ast::ImplPolarity::Positive
6780 // Parse both types and traits as a type, then reinterpret if necessary.
6781 let err_path = |span| ast::Path::from_ident(Ident::new(keywords::Invalid.name(), span));
6782 let ty_first = if self.token.is_keyword(keywords::For) &&
6783 self.look_ahead(1, |t| t != &token::Lt) {
6784 let span = self.prev_span.between(self.span);
6785 self.struct_span_err(span, "missing trait in a trait impl").emit();
6786 P(Ty { node: TyKind::Path(None, err_path(span)), span, id: ast::DUMMY_NODE_ID })
6791 // If `for` is missing we try to recover.
6792 let has_for = self.eat_keyword(keywords::For);
6793 let missing_for_span = self.prev_span.between(self.span);
6795 let ty_second = if self.token == token::DotDot {
6796 // We need to report this error after `cfg` expansion for compatibility reasons
6797 self.bump(); // `..`, do not add it to expected tokens
6798 Some(DummyResult::raw_ty(self.prev_span, true))
6799 } else if has_for || self.token.can_begin_type() {
6800 Some(self.parse_ty()?)
6805 generics.where_clause = self.parse_where_clause()?;
6807 let (impl_items, attrs) = self.parse_impl_body()?;
6809 let item_kind = match ty_second {
6810 Some(ty_second) => {
6811 // impl Trait for Type
6813 self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
6814 .span_suggestion_short(
6817 " for ".to_string(),
6818 Applicability::MachineApplicable,
6822 let ty_first = ty_first.into_inner();
6823 let path = match ty_first.node {
6824 // This notably includes paths passed through `ty` macro fragments (#46438).
6825 TyKind::Path(None, path) => path,
6827 self.span_err(ty_first.span, "expected a trait, found type");
6828 err_path(ty_first.span)
6831 let trait_ref = TraitRef { path, ref_id: ty_first.id };
6833 ItemKind::Impl(unsafety, polarity, defaultness,
6834 generics, Some(trait_ref), ty_second, impl_items)
6838 ItemKind::Impl(unsafety, polarity, defaultness,
6839 generics, None, ty_first, impl_items)
6843 Ok((keywords::Invalid.ident(), item_kind, Some(attrs)))
6846 fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
6847 if self.eat_keyword(keywords::For) {
6849 let params = self.parse_generic_params()?;
6851 // We rely on AST validation to rule out invalid cases: There must not be type
6852 // parameters, and the lifetime parameters must not have bounds.
6859 /// Parses `struct Foo { ... }`.
6860 fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
6861 let class_name = self.parse_ident()?;
6863 let mut generics = self.parse_generics()?;
6865 // There is a special case worth noting here, as reported in issue #17904.
6866 // If we are parsing a tuple struct it is the case that the where clause
6867 // should follow the field list. Like so:
6869 // struct Foo<T>(T) where T: Copy;
6871 // If we are parsing a normal record-style struct it is the case
6872 // that the where clause comes before the body, and after the generics.
6873 // So if we look ahead and see a brace or a where-clause we begin
6874 // parsing a record style struct.
6876 // Otherwise if we look ahead and see a paren we parse a tuple-style
6879 let vdata = if self.token.is_keyword(keywords::Where) {
6880 generics.where_clause = self.parse_where_clause()?;
6881 if self.eat(&token::Semi) {
6882 // If we see a: `struct Foo<T> where T: Copy;` style decl.
6883 VariantData::Unit(ast::DUMMY_NODE_ID)
6885 // If we see: `struct Foo<T> where T: Copy { ... }`
6886 let (fields, recovered) = self.parse_record_struct_body()?;
6887 VariantData::Struct(fields, recovered)
6889 // No `where` so: `struct Foo<T>;`
6890 } else if self.eat(&token::Semi) {
6891 VariantData::Unit(ast::DUMMY_NODE_ID)
6892 // Record-style struct definition
6893 } else if self.token == token::OpenDelim(token::Brace) {
6894 let (fields, recovered) = self.parse_record_struct_body()?;
6895 VariantData::Struct(fields, recovered)
6896 // Tuple-style struct definition with optional where-clause.
6897 } else if self.token == token::OpenDelim(token::Paren) {
6898 let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID);
6899 generics.where_clause = self.parse_where_clause()?;
6900 self.expect(&token::Semi)?;
6903 let token_str = self.this_token_descr();
6904 let mut err = self.fatal(&format!(
6905 "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
6908 err.span_label(self.span, "expected `where`, `{`, `(`, or `;` after struct name");
6912 Ok((class_name, ItemKind::Struct(vdata, generics), None))
6915 /// Parses `union Foo { ... }`.
6916 fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
6917 let class_name = self.parse_ident()?;
6919 let mut generics = self.parse_generics()?;
6921 let vdata = if self.token.is_keyword(keywords::Where) {
6922 generics.where_clause = self.parse_where_clause()?;
6923 let (fields, recovered) = self.parse_record_struct_body()?;
6924 VariantData::Struct(fields, recovered)
6925 } else if self.token == token::OpenDelim(token::Brace) {
6926 let (fields, recovered) = self.parse_record_struct_body()?;
6927 VariantData::Struct(fields, recovered)
6929 let token_str = self.this_token_descr();
6930 let mut err = self.fatal(&format!(
6931 "expected `where` or `{{` after union name, found {}", token_str));
6932 err.span_label(self.span, "expected `where` or `{` after union name");
6936 Ok((class_name, ItemKind::Union(vdata, generics), None))
6939 fn consume_block(&mut self, delim: token::DelimToken) {
6940 let mut brace_depth = 0;
6942 if self.eat(&token::OpenDelim(delim)) {
6944 } else if self.eat(&token::CloseDelim(delim)) {
6945 if brace_depth == 0 {
6951 } else if self.token == token::Eof || self.eat(&token::CloseDelim(token::NoDelim)) {
6959 fn parse_record_struct_body(
6961 ) -> PResult<'a, (Vec<StructField>, /* recovered */ bool)> {
6962 let mut fields = Vec::new();
6963 let mut recovered = false;
6964 if self.eat(&token::OpenDelim(token::Brace)) {
6965 while self.token != token::CloseDelim(token::Brace) {
6966 let field = self.parse_struct_decl_field().map_err(|e| {
6967 self.recover_stmt();
6972 Ok(field) => fields.push(field),
6978 self.eat(&token::CloseDelim(token::Brace));
6980 let token_str = self.this_token_descr();
6981 let mut err = self.fatal(&format!(
6982 "expected `where`, or `{{` after struct name, found {}", token_str));
6983 err.span_label(self.span, "expected `where`, or `{` after struct name");
6987 Ok((fields, recovered))
6990 fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
6991 // This is the case where we find `struct Foo<T>(T) where T: Copy;`
6992 // Unit like structs are handled in parse_item_struct function
6993 let fields = self.parse_unspanned_seq(
6994 &token::OpenDelim(token::Paren),
6995 &token::CloseDelim(token::Paren),
6996 SeqSep::trailing_allowed(token::Comma),
6998 let attrs = p.parse_outer_attributes()?;
7000 let vis = p.parse_visibility(true)?;
7001 let ty = p.parse_ty()?;
7003 span: lo.to(ty.span),
7006 id: ast::DUMMY_NODE_ID,
7015 /// Parses a structure field declaration.
7016 fn parse_single_struct_field(&mut self,
7019 attrs: Vec<Attribute> )
7020 -> PResult<'a, StructField> {
7021 let mut seen_comma: bool = false;
7022 let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
7023 if self.token == token::Comma {
7030 token::CloseDelim(token::Brace) => {}
7031 token::DocComment(_) => {
7032 let previous_span = self.prev_span;
7033 let mut err = self.span_fatal_err(self.span, Error::UselessDocComment);
7034 self.bump(); // consume the doc comment
7035 let comma_after_doc_seen = self.eat(&token::Comma);
7036 // `seen_comma` is always false, because we are inside doc block
7037 // condition is here to make code more readable
7038 if seen_comma == false && comma_after_doc_seen == true {
7041 if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
7044 if seen_comma == false {
7045 let sp = self.sess.source_map().next_point(previous_span);
7046 err.span_suggestion(
7048 "missing comma here",
7050 Applicability::MachineApplicable
7057 let sp = self.sess.source_map().next_point(self.prev_span);
7058 let mut err = self.struct_span_err(sp, &format!("expected `,`, or `}}`, found {}",
7059 self.this_token_descr()));
7060 if self.token.is_ident() {
7061 // This is likely another field; emit the diagnostic and keep going
7062 err.span_suggestion(
7064 "try adding a comma",
7066 Applicability::MachineApplicable,
7077 /// Parses an element of a struct declaration.
7078 fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
7079 let attrs = self.parse_outer_attributes()?;
7081 let vis = self.parse_visibility(false)?;
7082 self.parse_single_struct_field(lo, vis, attrs)
7085 /// Parses `pub`, `pub(crate)` and `pub(in path)` plus shortcuts `crate` for `pub(crate)`,
7086 /// `pub(self)` for `pub(in self)` and `pub(super)` for `pub(in super)`.
7087 /// If the following element can't be a tuple (i.e., it's a function definition), then
7088 /// it's not a tuple struct field), and the contents within the parentheses isn't valid,
7089 /// so emit a proper diagnostic.
7090 pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
7091 maybe_whole!(self, NtVis, |x| x);
7093 self.expected_tokens.push(TokenType::Keyword(keywords::Crate));
7094 if self.is_crate_vis() {
7095 self.bump(); // `crate`
7096 return Ok(respan(self.prev_span, VisibilityKind::Crate(CrateSugar::JustCrate)));
7099 if !self.eat_keyword(keywords::Pub) {
7100 // We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
7101 // keyword to grab a span from for inherited visibility; an empty span at the
7102 // beginning of the current token would seem to be the "Schelling span".
7103 return Ok(respan(self.span.shrink_to_lo(), VisibilityKind::Inherited))
7105 let lo = self.prev_span;
7107 if self.check(&token::OpenDelim(token::Paren)) {
7108 // We don't `self.bump()` the `(` yet because this might be a struct definition where
7109 // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
7110 // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
7111 // by the following tokens.
7112 if self.look_ahead(1, |t| t.is_keyword(keywords::Crate)) {
7115 self.bump(); // `crate`
7116 self.expect(&token::CloseDelim(token::Paren))?; // `)`
7118 lo.to(self.prev_span),
7119 VisibilityKind::Crate(CrateSugar::PubCrate),
7122 } else if self.look_ahead(1, |t| t.is_keyword(keywords::In)) {
7125 self.bump(); // `in`
7126 let path = self.parse_path(PathStyle::Mod)?; // `path`
7127 self.expect(&token::CloseDelim(token::Paren))?; // `)`
7128 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
7130 id: ast::DUMMY_NODE_ID,
7133 } else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) &&
7134 self.look_ahead(1, |t| t.is_keyword(keywords::Super) ||
7135 t.is_keyword(keywords::SelfLower))
7137 // `pub(self)` or `pub(super)`
7139 let path = self.parse_path(PathStyle::Mod)?; // `super`/`self`
7140 self.expect(&token::CloseDelim(token::Paren))?; // `)`
7141 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
7143 id: ast::DUMMY_NODE_ID,
7146 } else if !can_take_tuple { // Provide this diagnostic if this is not a tuple struct
7147 // `pub(something) fn ...` or `struct X { pub(something) y: Z }`
7149 let msg = "incorrect visibility restriction";
7150 let suggestion = r##"some possible visibility restrictions are:
7151 `pub(crate)`: visible only on the current crate
7152 `pub(super)`: visible only in the current module's parent
7153 `pub(in path::to::module)`: visible only on the specified path"##;
7154 let path = self.parse_path(PathStyle::Mod)?;
7155 let sp = self.prev_span;
7156 let help_msg = format!("make this visible only to module `{}` with `in`", path);
7157 self.expect(&token::CloseDelim(token::Paren))?; // `)`
7158 let mut err = struct_span_err!(self.sess.span_diagnostic, sp, E0704, "{}", msg);
7159 err.help(suggestion);
7160 err.span_suggestion(
7161 sp, &help_msg, format!("in {}", path), Applicability::MachineApplicable
7163 err.emit(); // emit diagnostic, but continue with public visibility
7167 Ok(respan(lo, VisibilityKind::Public))
7170 /// Parses defaultness (i.e., `default` or nothing).
7171 fn parse_defaultness(&mut self) -> Defaultness {
7172 // `pub` is included for better error messages
7173 if self.check_keyword(keywords::Default) &&
7174 self.look_ahead(1, |t| t.is_keyword(keywords::Impl) ||
7175 t.is_keyword(keywords::Const) ||
7176 t.is_keyword(keywords::Fn) ||
7177 t.is_keyword(keywords::Unsafe) ||
7178 t.is_keyword(keywords::Extern) ||
7179 t.is_keyword(keywords::Type) ||
7180 t.is_keyword(keywords::Pub)) {
7181 self.bump(); // `default`
7182 Defaultness::Default
7188 fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
7189 if self.eat(&token::Semi) {
7190 let mut err = self.struct_span_err(self.prev_span, "expected item, found `;`");
7191 err.span_suggestion_short(
7193 "remove this semicolon",
7195 Applicability::MachineApplicable,
7197 if !items.is_empty() {
7198 let previous_item = &items[items.len()-1];
7199 let previous_item_kind_name = match previous_item.node {
7200 // say "braced struct" because tuple-structs and
7201 // braceless-empty-struct declarations do take a semicolon
7202 ItemKind::Struct(..) => Some("braced struct"),
7203 ItemKind::Enum(..) => Some("enum"),
7204 ItemKind::Trait(..) => Some("trait"),
7205 ItemKind::Union(..) => Some("union"),
7208 if let Some(name) = previous_item_kind_name {
7209 err.help(&format!("{} declarations are not followed by a semicolon", name));
7219 /// Given a termination token, parses all of the items in a module.
7220 fn parse_mod_items(&mut self, term: &token::Token, inner_lo: Span) -> PResult<'a, Mod> {
7221 let mut items = vec![];
7222 while let Some(item) = self.parse_item()? {
7224 self.maybe_consume_incorrect_semicolon(&items);
7227 if !self.eat(term) {
7228 let token_str = self.this_token_descr();
7229 if !self.maybe_consume_incorrect_semicolon(&items) {
7230 let mut err = self.fatal(&format!("expected item, found {}", token_str));
7231 err.span_label(self.span, "expected item");
7236 let hi = if self.span.is_dummy() {
7243 inner: inner_lo.to(hi),
7249 fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
7250 let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
7251 self.expect(&token::Colon)?;
7252 let ty = self.parse_ty()?;
7253 self.expect(&token::Eq)?;
7254 let e = self.parse_expr()?;
7255 self.expect(&token::Semi)?;
7256 let item = match m {
7257 Some(m) => ItemKind::Static(ty, m, e),
7258 None => ItemKind::Const(ty, e),
7260 Ok((id, item, None))
7263 /// Parse a `mod <foo> { ... }` or `mod <foo>;` item
7264 fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
7265 let (in_cfg, outer_attrs) = {
7266 let mut strip_unconfigured = crate::config::StripUnconfigured {
7268 features: None, // don't perform gated feature checking
7270 let mut outer_attrs = outer_attrs.to_owned();
7271 strip_unconfigured.process_cfg_attrs(&mut outer_attrs);
7272 (!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
7275 let id_span = self.span;
7276 let id = self.parse_ident()?;
7277 if self.eat(&token::Semi) {
7278 if in_cfg && self.recurse_into_file_modules {
7279 // This mod is in an external file. Let's go get it!
7280 let ModulePathSuccess { path, directory_ownership, warn } =
7281 self.submod_path(id, &outer_attrs, id_span)?;
7282 let (module, mut attrs) =
7283 self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
7284 // Record that we fetched the mod from an external file
7286 let attr = Attribute {
7287 id: attr::mk_attr_id(),
7288 style: ast::AttrStyle::Outer,
7289 path: ast::Path::from_ident(Ident::from_str("warn_directory_ownership")),
7290 tokens: TokenStream::empty(),
7291 is_sugared_doc: false,
7292 span: syntax_pos::DUMMY_SP,
7294 attr::mark_known(&attr);
7297 Ok((id, ItemKind::Mod(module), Some(attrs)))
7299 let placeholder = ast::Mod {
7300 inner: syntax_pos::DUMMY_SP,
7304 Ok((id, ItemKind::Mod(placeholder), None))
7307 let old_directory = self.directory.clone();
7308 self.push_directory(id, &outer_attrs);
7310 self.expect(&token::OpenDelim(token::Brace))?;
7311 let mod_inner_lo = self.span;
7312 let attrs = self.parse_inner_attributes()?;
7313 let module = self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo)?;
7315 self.directory = old_directory;
7316 Ok((id, ItemKind::Mod(module), Some(attrs)))
7320 fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
7321 if let Some(path) = attr::first_attr_value_str_by_name(attrs, "path") {
7322 self.directory.path.to_mut().push(&path.as_str());
7323 self.directory.ownership = DirectoryOwnership::Owned { relative: None };
7325 // We have to push on the current module name in the case of relative
7326 // paths in order to ensure that any additional module paths from inline
7327 // `mod x { ... }` come after the relative extension.
7329 // For example, a `mod z { ... }` inside `x/y.rs` should set the current
7330 // directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`.
7331 if let DirectoryOwnership::Owned { relative } = &mut self.directory.ownership {
7332 if let Some(ident) = relative.take() { // remove the relative offset
7333 self.directory.path.to_mut().push(ident.as_str());
7336 self.directory.path.to_mut().push(&id.as_str());
7340 pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
7341 if let Some(s) = attr::first_attr_value_str_by_name(attrs, "path") {
7344 // On windows, the base path might have the form
7345 // `\\?\foo\bar` in which case it does not tolerate
7346 // mixed `/` and `\` separators, so canonicalize
7349 let s = s.replace("/", "\\");
7350 Some(dir_path.join(s))
7356 /// Returns a path to a module.
7357 pub fn default_submod_path(
7359 relative: Option<ast::Ident>,
7361 source_map: &SourceMap) -> ModulePath
7363 // If we're in a foo.rs file instead of a mod.rs file,
7364 // we need to look for submodules in
7365 // `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than
7366 // `./<id>.rs` and `./<id>/mod.rs`.
7367 let relative_prefix_string;
7368 let relative_prefix = if let Some(ident) = relative {
7369 relative_prefix_string = format!("{}{}", ident.as_str(), path::MAIN_SEPARATOR);
7370 &relative_prefix_string
7375 let mod_name = id.to_string();
7376 let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
7377 let secondary_path_str = format!("{}{}{}mod.rs",
7378 relative_prefix, mod_name, path::MAIN_SEPARATOR);
7379 let default_path = dir_path.join(&default_path_str);
7380 let secondary_path = dir_path.join(&secondary_path_str);
7381 let default_exists = source_map.file_exists(&default_path);
7382 let secondary_exists = source_map.file_exists(&secondary_path);
7384 let result = match (default_exists, secondary_exists) {
7385 (true, false) => Ok(ModulePathSuccess {
7387 directory_ownership: DirectoryOwnership::Owned {
7392 (false, true) => Ok(ModulePathSuccess {
7393 path: secondary_path,
7394 directory_ownership: DirectoryOwnership::Owned {
7399 (false, false) => Err(Error::FileNotFoundForModule {
7400 mod_name: mod_name.clone(),
7401 default_path: default_path_str,
7402 secondary_path: secondary_path_str,
7403 dir_path: dir_path.display().to_string(),
7405 (true, true) => Err(Error::DuplicatePaths {
7406 mod_name: mod_name.clone(),
7407 default_path: default_path_str,
7408 secondary_path: secondary_path_str,
7414 path_exists: default_exists || secondary_exists,
7419 fn submod_path(&mut self,
7421 outer_attrs: &[Attribute],
7423 -> PResult<'a, ModulePathSuccess> {
7424 if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) {
7425 return Ok(ModulePathSuccess {
7426 directory_ownership: match path.file_name().and_then(|s| s.to_str()) {
7427 // All `#[path]` files are treated as though they are a `mod.rs` file.
7428 // This means that `mod foo;` declarations inside `#[path]`-included
7429 // files are siblings,
7431 // Note that this will produce weirdness when a file named `foo.rs` is
7432 // `#[path]` included and contains a `mod foo;` declaration.
7433 // If you encounter this, it's your own darn fault :P
7434 Some(_) => DirectoryOwnership::Owned { relative: None },
7435 _ => DirectoryOwnership::UnownedViaMod(true),
7442 let relative = match self.directory.ownership {
7443 DirectoryOwnership::Owned { relative } => relative,
7444 DirectoryOwnership::UnownedViaBlock |
7445 DirectoryOwnership::UnownedViaMod(_) => None,
7447 let paths = Parser::default_submod_path(
7448 id, relative, &self.directory.path, self.sess.source_map());
7450 match self.directory.ownership {
7451 DirectoryOwnership::Owned { .. } => {
7452 paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
7454 DirectoryOwnership::UnownedViaBlock => {
7456 "Cannot declare a non-inline module inside a block \
7457 unless it has a path attribute";
7458 let mut err = self.diagnostic().struct_span_err(id_sp, msg);
7459 if paths.path_exists {
7460 let msg = format!("Maybe `use` the module `{}` instead of redeclaring it",
7462 err.span_note(id_sp, &msg);
7466 DirectoryOwnership::UnownedViaMod(warn) => {
7468 if let Ok(result) = paths.result {
7469 return Ok(ModulePathSuccess { warn: true, ..result });
7472 let mut err = self.diagnostic().struct_span_err(id_sp,
7473 "cannot declare a new module at this location");
7474 if !id_sp.is_dummy() {
7475 let src_path = self.sess.source_map().span_to_filename(id_sp);
7476 if let FileName::Real(src_path) = src_path {
7477 if let Some(stem) = src_path.file_stem() {
7478 let mut dest_path = src_path.clone();
7479 dest_path.set_file_name(stem);
7480 dest_path.push("mod.rs");
7481 err.span_note(id_sp,
7482 &format!("maybe move this module `{}` to its own \
7483 directory via `{}`", src_path.display(),
7484 dest_path.display()));
7488 if paths.path_exists {
7489 err.span_note(id_sp,
7490 &format!("... or maybe `use` the module `{}` instead \
7491 of possibly redeclaring it",
7499 /// Reads a module from a source file.
7500 fn eval_src_mod(&mut self,
7502 directory_ownership: DirectoryOwnership,
7505 -> PResult<'a, (ast::Mod, Vec<Attribute> )> {
7506 let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
7507 if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
7508 let mut err = String::from("circular modules: ");
7509 let len = included_mod_stack.len();
7510 for p in &included_mod_stack[i.. len] {
7511 err.push_str(&p.to_string_lossy());
7512 err.push_str(" -> ");
7514 err.push_str(&path.to_string_lossy());
7515 return Err(self.span_fatal(id_sp, &err[..]));
7517 included_mod_stack.push(path.clone());
7518 drop(included_mod_stack);
7521 new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp);
7522 p0.cfg_mods = self.cfg_mods;
7523 let mod_inner_lo = p0.span;
7524 let mod_attrs = p0.parse_inner_attributes()?;
7525 let mut m0 = p0.parse_mod_items(&token::Eof, mod_inner_lo)?;
7527 self.sess.included_mod_stack.borrow_mut().pop();
7531 /// Parses a function declaration from a foreign module.
7532 fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
7533 -> PResult<'a, ForeignItem> {
7534 self.expect_keyword(keywords::Fn)?;
7536 let (ident, mut generics) = self.parse_fn_header()?;
7537 let decl = self.parse_fn_decl(true)?;
7538 generics.where_clause = self.parse_where_clause()?;
7540 self.expect(&token::Semi)?;
7541 Ok(ast::ForeignItem {
7544 node: ForeignItemKind::Fn(decl, generics),
7545 id: ast::DUMMY_NODE_ID,
7551 /// Parses a static item from a foreign module.
7552 /// Assumes that the `static` keyword is already parsed.
7553 fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
7554 -> PResult<'a, ForeignItem> {
7555 let mutbl = self.eat_keyword(keywords::Mut);
7556 let ident = self.parse_ident()?;
7557 self.expect(&token::Colon)?;
7558 let ty = self.parse_ty()?;
7560 self.expect(&token::Semi)?;
7564 node: ForeignItemKind::Static(ty, mutbl),
7565 id: ast::DUMMY_NODE_ID,
7571 /// Parses a type from a foreign module.
7572 fn parse_item_foreign_type(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
7573 -> PResult<'a, ForeignItem> {
7574 self.expect_keyword(keywords::Type)?;
7576 let ident = self.parse_ident()?;
7578 self.expect(&token::Semi)?;
7579 Ok(ast::ForeignItem {
7582 node: ForeignItemKind::Ty,
7583 id: ast::DUMMY_NODE_ID,
7589 fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> {
7590 let error_msg = "crate name using dashes are not valid in `extern crate` statements";
7591 let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
7593 let mut ident = if self.token.is_keyword(keywords::SelfLower) {
7594 self.parse_path_segment_ident()
7598 let mut idents = vec![];
7599 let mut replacement = vec![];
7600 let mut fixed_crate_name = false;
7601 // Accept `extern crate name-like-this` for better diagnostics
7602 let dash = token::Token::BinOp(token::BinOpToken::Minus);
7603 if self.token == dash { // Do not include `-` as part of the expected tokens list
7604 while self.eat(&dash) {
7605 fixed_crate_name = true;
7606 replacement.push((self.prev_span, "_".to_string()));
7607 idents.push(self.parse_ident()?);
7610 if fixed_crate_name {
7611 let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
7612 let mut fixed_name = format!("{}", ident.name);
7613 for part in idents {
7614 fixed_name.push_str(&format!("_{}", part.name));
7616 ident = Ident::from_str(&fixed_name).with_span_pos(fixed_name_sp);
7618 let mut err = self.struct_span_err(fixed_name_sp, error_msg);
7619 err.span_label(fixed_name_sp, "dash-separated idents are not valid");
7620 err.multipart_suggestion(
7623 Applicability::MachineApplicable,
7630 /// Parses `extern crate` links.
7635 /// extern crate foo;
7636 /// extern crate bar as foo;
7638 fn parse_item_extern_crate(&mut self,
7640 visibility: Visibility,
7641 attrs: Vec<Attribute>)
7642 -> PResult<'a, P<Item>> {
7643 // Accept `extern crate name-like-this` for better diagnostics
7644 let orig_name = self.parse_crate_name_with_dashes()?;
7645 let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
7646 (rename, Some(orig_name.name))
7650 self.expect(&token::Semi)?;
7652 let span = lo.to(self.prev_span);
7653 Ok(self.mk_item(span, item_name, ItemKind::ExternCrate(orig_name), visibility, attrs))
7656 /// Parses `extern` for foreign ABIs modules.
7658 /// `extern` is expected to have been
7659 /// consumed before calling this method.
7663 /// ```ignore (only-for-syntax-highlight)
7667 fn parse_item_foreign_mod(&mut self,
7669 opt_abi: Option<Abi>,
7670 visibility: Visibility,
7671 mut attrs: Vec<Attribute>)
7672 -> PResult<'a, P<Item>> {
7673 self.expect(&token::OpenDelim(token::Brace))?;
7675 let abi = opt_abi.unwrap_or(Abi::C);
7677 attrs.extend(self.parse_inner_attributes()?);
7679 let mut foreign_items = vec![];
7680 while !self.eat(&token::CloseDelim(token::Brace)) {
7681 foreign_items.push(self.parse_foreign_item()?);
7684 let prev_span = self.prev_span;
7685 let m = ast::ForeignMod {
7687 items: foreign_items
7689 let invalid = keywords::Invalid.ident();
7690 Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
7693 /// Parses `type Foo = Bar;`
7695 /// `existential type Foo: Bar;`
7698 /// without modifying the parser state.
7699 fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, ast::Generics)>> {
7700 // This parses the grammar:
7701 // Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
7702 if self.check_keyword(keywords::Type) ||
7703 self.check_keyword(keywords::Existential) &&
7704 self.look_ahead(1, |t| t.is_keyword(keywords::Type)) {
7705 let existential = self.eat_keyword(keywords::Existential);
7706 assert!(self.eat_keyword(keywords::Type));
7707 Some(self.parse_existential_or_alias(existential))
7713 /// Parses a type alias or existential type.
7714 fn parse_existential_or_alias(
7717 ) -> PResult<'a, (Ident, AliasKind, ast::Generics)> {
7718 let ident = self.parse_ident()?;
7719 let mut tps = self.parse_generics()?;
7720 tps.where_clause = self.parse_where_clause()?;
7721 let alias = if existential {
7722 self.expect(&token::Colon)?;
7723 let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
7724 AliasKind::Existential(bounds)
7726 self.expect(&token::Eq)?;
7727 let ty = self.parse_ty()?;
7730 self.expect(&token::Semi)?;
7731 Ok((ident, alias, tps))
7734 /// Parses the part of an enum declaration following the `{`.
7735 fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
7736 let mut variants = Vec::new();
7737 let mut all_nullary = true;
7738 let mut any_disr = vec![];
7739 while self.token != token::CloseDelim(token::Brace) {
7740 let variant_attrs = self.parse_outer_attributes()?;
7741 let vlo = self.span;
7744 let mut disr_expr = None;
7746 let ident = self.parse_ident()?;
7747 if self.check(&token::OpenDelim(token::Brace)) {
7748 // Parse a struct variant.
7749 all_nullary = false;
7750 let (fields, recovered) = self.parse_record_struct_body()?;
7751 struct_def = VariantData::Struct(fields, recovered);
7752 } else if self.check(&token::OpenDelim(token::Paren)) {
7753 all_nullary = false;
7754 struct_def = VariantData::Tuple(
7755 self.parse_tuple_struct_body()?,
7758 } else if self.eat(&token::Eq) {
7759 disr_expr = Some(AnonConst {
7760 id: ast::DUMMY_NODE_ID,
7761 value: self.parse_expr()?,
7763 if let Some(sp) = disr_expr.as_ref().map(|c| c.value.span) {
7766 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
7768 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
7771 let vr = ast::Variant_ {
7773 id: ast::DUMMY_NODE_ID,
7774 attrs: variant_attrs,
7778 variants.push(respan(vlo.to(self.prev_span), vr));
7780 if !self.eat(&token::Comma) {
7781 if self.token.is_ident() && !self.token.is_reserved_ident() {
7782 let sp = self.sess.source_map().next_point(self.prev_span);
7783 let mut err = self.struct_span_err(sp, "missing comma");
7784 err.span_suggestion_short(
7788 Applicability::MaybeIncorrect,
7796 self.expect(&token::CloseDelim(token::Brace))?;
7797 if !any_disr.is_empty() && !all_nullary {
7798 let mut err = self.struct_span_err(
7800 "discriminator values can only be used with a field-less enum",
7802 for sp in any_disr {
7803 err.span_label(sp, "only valid in field-less enums");
7808 Ok(ast::EnumDef { variants })
7811 /// Parses an enum declaration.
7812 fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
7813 let id = self.parse_ident()?;
7814 let mut generics = self.parse_generics()?;
7815 generics.where_clause = self.parse_where_clause()?;
7816 self.expect(&token::OpenDelim(token::Brace))?;
7818 let enum_definition = self.parse_enum_def(&generics).map_err(|e| {
7819 self.recover_stmt();
7820 self.eat(&token::CloseDelim(token::Brace));
7823 Ok((id, ItemKind::Enum(enum_definition, generics), None))
7826 /// Parses a string as an ABI spec on an extern type or module. Consumes
7827 /// the `extern` keyword, if one is found.
7828 fn parse_opt_abi(&mut self) -> PResult<'a, Option<Abi>> {
7830 token::Literal(token::Str_(s), suf) | token::Literal(token::StrRaw(s, _), suf) => {
7832 self.expect_no_suffix(sp, "an ABI spec", suf);
7834 match abi::lookup(&s.as_str()) {
7835 Some(abi) => Ok(Some(abi)),
7837 let prev_span = self.prev_span;
7838 let mut err = struct_span_err!(
7839 self.sess.span_diagnostic,
7842 "invalid ABI: found `{}`",
7844 err.span_label(prev_span, "invalid ABI");
7845 err.help(&format!("valid ABIs: {}", abi::all_names().join(", ")));
7856 fn is_static_global(&mut self) -> bool {
7857 if self.check_keyword(keywords::Static) {
7858 // Check if this could be a closure
7859 !self.look_ahead(1, |token| {
7860 if token.is_keyword(keywords::Move) {
7864 token::BinOp(token::Or) | token::OrOr => true,
7875 attrs: Vec<Attribute>,
7876 macros_allowed: bool,
7877 attributes_allowed: bool,
7878 ) -> PResult<'a, Option<P<Item>>> {
7879 let mut unclosed_delims = vec![];
7880 let (ret, tokens) = self.collect_tokens(|this| {
7881 let item = this.parse_item_implementation(attrs, macros_allowed, attributes_allowed);
7882 unclosed_delims.append(&mut this.unclosed_delims);
7885 self.unclosed_delims.append(&mut unclosed_delims);
7887 // Once we've parsed an item and recorded the tokens we got while
7888 // parsing we may want to store `tokens` into the item we're about to
7889 // return. Note, though, that we specifically didn't capture tokens
7890 // related to outer attributes. The `tokens` field here may later be
7891 // used with procedural macros to convert this item back into a token
7892 // stream, but during expansion we may be removing attributes as we go
7895 // If we've got inner attributes then the `tokens` we've got above holds
7896 // these inner attributes. If an inner attribute is expanded we won't
7897 // actually remove it from the token stream, so we'll just keep yielding
7898 // it (bad!). To work around this case for now we just avoid recording
7899 // `tokens` if we detect any inner attributes. This should help keep
7900 // expansion correct, but we should fix this bug one day!
7903 if !i.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
7904 i.tokens = Some(tokens);
7911 /// Parses one of the items allowed by the flags.
7912 fn parse_item_implementation(
7914 attrs: Vec<Attribute>,
7915 macros_allowed: bool,
7916 attributes_allowed: bool,
7917 ) -> PResult<'a, Option<P<Item>>> {
7918 maybe_whole!(self, NtItem, |item| {
7919 let mut item = item.into_inner();
7920 let mut attrs = attrs;
7921 mem::swap(&mut item.attrs, &mut attrs);
7922 item.attrs.extend(attrs);
7928 let visibility = self.parse_visibility(false)?;
7930 if self.eat_keyword(keywords::Use) {
7932 let item_ = ItemKind::Use(P(self.parse_use_tree()?));
7933 self.expect(&token::Semi)?;
7935 let span = lo.to(self.prev_span);
7936 let item = self.mk_item(span, keywords::Invalid.ident(), item_, visibility, attrs);
7937 return Ok(Some(item));
7940 if self.eat_keyword(keywords::Extern) {
7941 if self.eat_keyword(keywords::Crate) {
7942 return Ok(Some(self.parse_item_extern_crate(lo, visibility, attrs)?));
7945 let opt_abi = self.parse_opt_abi()?;
7947 if self.eat_keyword(keywords::Fn) {
7948 // EXTERN FUNCTION ITEM
7949 let fn_span = self.prev_span;
7950 let abi = opt_abi.unwrap_or(Abi::C);
7951 let (ident, item_, extra_attrs) =
7952 self.parse_item_fn(Unsafety::Normal,
7953 respan(fn_span, IsAsync::NotAsync),
7954 respan(fn_span, Constness::NotConst),
7956 let prev_span = self.prev_span;
7957 let item = self.mk_item(lo.to(prev_span),
7961 maybe_append(attrs, extra_attrs));
7962 return Ok(Some(item));
7963 } else if self.check(&token::OpenDelim(token::Brace)) {
7964 return Ok(Some(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs)?));
7970 if self.is_static_global() {
7973 let m = if self.eat_keyword(keywords::Mut) {
7976 Mutability::Immutable
7978 let (ident, item_, extra_attrs) = self.parse_item_const(Some(m))?;
7979 let prev_span = self.prev_span;
7980 let item = self.mk_item(lo.to(prev_span),
7984 maybe_append(attrs, extra_attrs));
7985 return Ok(Some(item));
7987 if self.eat_keyword(keywords::Const) {
7988 let const_span = self.prev_span;
7989 if self.check_keyword(keywords::Fn)
7990 || (self.check_keyword(keywords::Unsafe)
7991 && self.look_ahead(1, |t| t.is_keyword(keywords::Fn))) {
7992 // CONST FUNCTION ITEM
7993 let unsafety = self.parse_unsafety();
7995 let (ident, item_, extra_attrs) =
7996 self.parse_item_fn(unsafety,
7997 respan(const_span, IsAsync::NotAsync),
7998 respan(const_span, Constness::Const),
8000 let prev_span = self.prev_span;
8001 let item = self.mk_item(lo.to(prev_span),
8005 maybe_append(attrs, extra_attrs));
8006 return Ok(Some(item));
8010 if self.eat_keyword(keywords::Mut) {
8011 let prev_span = self.prev_span;
8012 let mut err = self.diagnostic()
8013 .struct_span_err(prev_span, "const globals cannot be mutable");
8014 err.span_label(prev_span, "cannot be mutable");
8015 err.span_suggestion(
8017 "you might want to declare a static instead",
8018 "static".to_owned(),
8019 Applicability::MaybeIncorrect,
8023 let (ident, item_, extra_attrs) = self.parse_item_const(None)?;
8024 let prev_span = self.prev_span;
8025 let item = self.mk_item(lo.to(prev_span),
8029 maybe_append(attrs, extra_attrs));
8030 return Ok(Some(item));
8033 // `unsafe async fn` or `async fn`
8035 self.check_keyword(keywords::Unsafe) &&
8036 self.look_ahead(1, |t| t.is_keyword(keywords::Async))
8038 self.check_keyword(keywords::Async) &&
8039 self.look_ahead(1, |t| t.is_keyword(keywords::Fn))
8042 // ASYNC FUNCTION ITEM
8043 let unsafety = self.parse_unsafety();
8044 self.expect_keyword(keywords::Async)?;
8045 let async_span = self.prev_span;
8046 self.expect_keyword(keywords::Fn)?;
8047 let fn_span = self.prev_span;
8048 let (ident, item_, extra_attrs) =
8049 self.parse_item_fn(unsafety,
8050 respan(async_span, IsAsync::Async {
8051 closure_id: ast::DUMMY_NODE_ID,
8052 return_impl_trait_id: ast::DUMMY_NODE_ID,
8054 respan(fn_span, Constness::NotConst),
8056 let prev_span = self.prev_span;
8057 let item = self.mk_item(lo.to(prev_span),
8061 maybe_append(attrs, extra_attrs));
8062 if self.span.rust_2015() {
8063 self.diagnostic().struct_span_err_with_code(
8065 "`async fn` is not permitted in the 2015 edition",
8066 DiagnosticId::Error("E0670".into())
8069 return Ok(Some(item));
8071 if self.check_keyword(keywords::Unsafe) &&
8072 (self.look_ahead(1, |t| t.is_keyword(keywords::Trait)) ||
8073 self.look_ahead(1, |t| t.is_keyword(keywords::Auto)))
8075 // UNSAFE TRAIT ITEM
8076 self.bump(); // `unsafe`
8077 let is_auto = if self.eat_keyword(keywords::Trait) {
8080 self.expect_keyword(keywords::Auto)?;
8081 self.expect_keyword(keywords::Trait)?;
8084 let (ident, item_, extra_attrs) =
8085 self.parse_item_trait(is_auto, Unsafety::Unsafe)?;
8086 let prev_span = self.prev_span;
8087 let item = self.mk_item(lo.to(prev_span),
8091 maybe_append(attrs, extra_attrs));
8092 return Ok(Some(item));
8094 if self.check_keyword(keywords::Impl) ||
8095 self.check_keyword(keywords::Unsafe) &&
8096 self.look_ahead(1, |t| t.is_keyword(keywords::Impl)) ||
8097 self.check_keyword(keywords::Default) &&
8098 self.look_ahead(1, |t| t.is_keyword(keywords::Impl)) ||
8099 self.check_keyword(keywords::Default) &&
8100 self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe)) {
8102 let defaultness = self.parse_defaultness();
8103 let unsafety = self.parse_unsafety();
8104 self.expect_keyword(keywords::Impl)?;
8105 let (ident, item, extra_attrs) = self.parse_item_impl(unsafety, defaultness)?;
8106 let span = lo.to(self.prev_span);
8107 return Ok(Some(self.mk_item(span, ident, item, visibility,
8108 maybe_append(attrs, extra_attrs))));
8110 if self.check_keyword(keywords::Fn) {
8113 let fn_span = self.prev_span;
8114 let (ident, item_, extra_attrs) =
8115 self.parse_item_fn(Unsafety::Normal,
8116 respan(fn_span, IsAsync::NotAsync),
8117 respan(fn_span, Constness::NotConst),
8119 let prev_span = self.prev_span;
8120 let item = self.mk_item(lo.to(prev_span),
8124 maybe_append(attrs, extra_attrs));
8125 return Ok(Some(item));
8127 if self.check_keyword(keywords::Unsafe)
8128 && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
8129 // UNSAFE FUNCTION ITEM
8130 self.bump(); // `unsafe`
8131 // `{` is also expected after `unsafe`, in case of error, include it in the diagnostic
8132 self.check(&token::OpenDelim(token::Brace));
8133 let abi = if self.eat_keyword(keywords::Extern) {
8134 self.parse_opt_abi()?.unwrap_or(Abi::C)
8138 self.expect_keyword(keywords::Fn)?;
8139 let fn_span = self.prev_span;
8140 let (ident, item_, extra_attrs) =
8141 self.parse_item_fn(Unsafety::Unsafe,
8142 respan(fn_span, IsAsync::NotAsync),
8143 respan(fn_span, Constness::NotConst),
8145 let prev_span = self.prev_span;
8146 let item = self.mk_item(lo.to(prev_span),
8150 maybe_append(attrs, extra_attrs));
8151 return Ok(Some(item));
8153 if self.eat_keyword(keywords::Mod) {
8155 let (ident, item_, extra_attrs) =
8156 self.parse_item_mod(&attrs[..])?;
8157 let prev_span = self.prev_span;
8158 let item = self.mk_item(lo.to(prev_span),
8162 maybe_append(attrs, extra_attrs));
8163 return Ok(Some(item));
8165 if let Some(type_) = self.eat_type() {
8166 let (ident, alias, generics) = type_?;
8168 let item_ = match alias {
8169 AliasKind::Weak(ty) => ItemKind::Ty(ty, generics),
8170 AliasKind::Existential(bounds) => ItemKind::Existential(bounds, generics),
8172 let prev_span = self.prev_span;
8173 let item = self.mk_item(lo.to(prev_span),
8178 return Ok(Some(item));
8180 if self.eat_keyword(keywords::Enum) {
8182 let (ident, item_, extra_attrs) = self.parse_item_enum()?;
8183 let prev_span = self.prev_span;
8184 let item = self.mk_item(lo.to(prev_span),
8188 maybe_append(attrs, extra_attrs));
8189 return Ok(Some(item));
8191 if self.check_keyword(keywords::Trait)
8192 || (self.check_keyword(keywords::Auto)
8193 && self.look_ahead(1, |t| t.is_keyword(keywords::Trait)))
8195 let is_auto = if self.eat_keyword(keywords::Trait) {
8198 self.expect_keyword(keywords::Auto)?;
8199 self.expect_keyword(keywords::Trait)?;
8203 let (ident, item_, extra_attrs) =
8204 self.parse_item_trait(is_auto, Unsafety::Normal)?;
8205 let prev_span = self.prev_span;
8206 let item = self.mk_item(lo.to(prev_span),
8210 maybe_append(attrs, extra_attrs));
8211 return Ok(Some(item));
8213 if self.eat_keyword(keywords::Struct) {
8215 let (ident, item_, extra_attrs) = self.parse_item_struct()?;
8216 let prev_span = self.prev_span;
8217 let item = self.mk_item(lo.to(prev_span),
8221 maybe_append(attrs, extra_attrs));
8222 return Ok(Some(item));
8224 if self.is_union_item() {
8227 let (ident, item_, extra_attrs) = self.parse_item_union()?;
8228 let prev_span = self.prev_span;
8229 let item = self.mk_item(lo.to(prev_span),
8233 maybe_append(attrs, extra_attrs));
8234 return Ok(Some(item));
8236 if let Some(macro_def) = self.eat_macro_def(&attrs, &visibility, lo)? {
8237 return Ok(Some(macro_def));
8240 // Verify whether we have encountered a struct or method definition where the user forgot to
8241 // add the `struct` or `fn` keyword after writing `pub`: `pub S {}`
8242 if visibility.node.is_pub() &&
8243 self.check_ident() &&
8244 self.look_ahead(1, |t| *t != token::Not)
8246 // Space between `pub` keyword and the identifier
8249 // ^^^ `sp` points here
8250 let sp = self.prev_span.between(self.span);
8251 let full_sp = self.prev_span.to(self.span);
8252 let ident_sp = self.span;
8253 if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
8254 // possible public struct definition where `struct` was forgotten
8255 let ident = self.parse_ident().unwrap();
8256 let msg = format!("add `struct` here to parse `{}` as a public struct",
8258 let mut err = self.diagnostic()
8259 .struct_span_err(sp, "missing `struct` for struct definition");
8260 err.span_suggestion_short(
8261 sp, &msg, " struct ".into(), Applicability::MaybeIncorrect // speculative
8264 } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
8265 let ident = self.parse_ident().unwrap();
8267 let kw_name = if let Ok(Some(_)) = self.parse_self_arg() {
8272 self.consume_block(token::Paren);
8273 let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
8274 self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
8276 ("fn", kw_name, false)
8277 } else if self.check(&token::OpenDelim(token::Brace)) {
8279 ("fn", kw_name, false)
8280 } else if self.check(&token::Colon) {
8284 ("fn` or `struct", "function or struct", true)
8286 self.consume_block(token::Brace);
8288 let msg = format!("missing `{}` for {} definition", kw, kw_name);
8289 let mut err = self.diagnostic().struct_span_err(sp, &msg);
8291 let suggestion = format!("add `{}` here to parse `{}` as a public {}",
8295 err.span_suggestion_short(
8296 sp, &suggestion, format!(" {} ", kw), Applicability::MachineApplicable
8299 if let Ok(snippet) = self.sess.source_map().span_to_snippet(ident_sp) {
8300 err.span_suggestion(
8302 "if you meant to call a macro, try",
8303 format!("{}!", snippet),
8304 // this is the `ambiguous` conditional branch
8305 Applicability::MaybeIncorrect
8308 err.help("if you meant to call a macro, remove the `pub` \
8309 and add a trailing `!` after the identifier");
8313 } else if self.look_ahead(1, |t| *t == token::Lt) {
8314 let ident = self.parse_ident().unwrap();
8315 self.eat_to_tokens(&[&token::Gt]);
8317 let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
8318 if let Ok(Some(_)) = self.parse_self_arg() {
8319 ("fn", "method", false)
8321 ("fn", "function", false)
8323 } else if self.check(&token::OpenDelim(token::Brace)) {
8324 ("struct", "struct", false)
8326 ("fn` or `struct", "function or struct", true)
8328 let msg = format!("missing `{}` for {} definition", kw, kw_name);
8329 let mut err = self.diagnostic().struct_span_err(sp, &msg);
8331 err.span_suggestion_short(
8333 &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
8334 format!(" {} ", kw),
8335 Applicability::MachineApplicable,
8341 self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility)
8344 /// Parses a foreign item.
8345 crate fn parse_foreign_item(&mut self) -> PResult<'a, ForeignItem> {
8346 maybe_whole!(self, NtForeignItem, |ni| ni);
8348 let attrs = self.parse_outer_attributes()?;
8350 let visibility = self.parse_visibility(false)?;
8352 // FOREIGN STATIC ITEM
8353 // Treat `const` as `static` for error recovery, but don't add it to expected tokens.
8354 if self.check_keyword(keywords::Static) || self.token.is_keyword(keywords::Const) {
8355 if self.token.is_keyword(keywords::Const) {
8357 .struct_span_err(self.span, "extern items cannot be `const`")
8360 "try using a static value",
8361 "static".to_owned(),
8362 Applicability::MachineApplicable
8365 self.bump(); // `static` or `const`
8366 return Ok(self.parse_item_foreign_static(visibility, lo, attrs)?);
8368 // FOREIGN FUNCTION ITEM
8369 if self.check_keyword(keywords::Fn) {
8370 return Ok(self.parse_item_foreign_fn(visibility, lo, attrs)?);
8372 // FOREIGN TYPE ITEM
8373 if self.check_keyword(keywords::Type) {
8374 return Ok(self.parse_item_foreign_type(visibility, lo, attrs)?);
8377 match self.parse_assoc_macro_invoc("extern", Some(&visibility), &mut false)? {
8381 ident: keywords::Invalid.ident(),
8382 span: lo.to(self.prev_span),
8383 id: ast::DUMMY_NODE_ID,
8386 node: ForeignItemKind::Macro(mac),
8391 if !attrs.is_empty() {
8392 self.expected_item_err(&attrs)?;
8400 /// This is the fall-through for parsing items.
8401 fn parse_macro_use_or_failure(
8403 attrs: Vec<Attribute> ,
8404 macros_allowed: bool,
8405 attributes_allowed: bool,
8407 visibility: Visibility
8408 ) -> PResult<'a, Option<P<Item>>> {
8409 if macros_allowed && self.token.is_path_start() &&
8410 !(self.is_async_fn() && self.span.rust_2015()) {
8411 // MACRO INVOCATION ITEM
8413 let prev_span = self.prev_span;
8414 self.complain_if_pub_macro(&visibility.node, prev_span);
8416 let mac_lo = self.span;
8419 let pth = self.parse_path(PathStyle::Mod)?;
8420 self.expect(&token::Not)?;
8422 // a 'special' identifier (like what `macro_rules!` uses)
8423 // is optional. We should eventually unify invoc syntax
8425 let id = if self.token.is_ident() {
8428 keywords::Invalid.ident() // no special identifier
8430 // eat a matched-delimiter token tree:
8431 let (delim, tts) = self.expect_delimited_token_tree()?;
8432 if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
8433 self.report_invalid_macro_expansion_item();
8436 let hi = self.prev_span;
8437 let mac = respan(mac_lo.to(hi), Mac_ { path: pth, tts, delim });
8438 let item = self.mk_item(lo.to(hi), id, ItemKind::Mac(mac), visibility, attrs);
8439 return Ok(Some(item));
8442 // FAILURE TO PARSE ITEM
8443 match visibility.node {
8444 VisibilityKind::Inherited => {}
8446 return Err(self.span_fatal(self.prev_span, "unmatched visibility `pub`"));
8450 if !attributes_allowed && !attrs.is_empty() {
8451 self.expected_item_err(&attrs)?;
8456 /// Parses a macro invocation inside a `trait`, `impl` or `extern` block.
8457 fn parse_assoc_macro_invoc(&mut self, item_kind: &str, vis: Option<&Visibility>,
8458 at_end: &mut bool) -> PResult<'a, Option<Mac>>
8460 if self.token.is_path_start() &&
8461 !(self.is_async_fn() && self.span.rust_2015()) {
8462 let prev_span = self.prev_span;
8464 let pth = self.parse_path(PathStyle::Mod)?;
8466 if pth.segments.len() == 1 {
8467 if !self.eat(&token::Not) {
8468 return Err(self.missing_assoc_item_kind_err(item_kind, prev_span));
8471 self.expect(&token::Not)?;
8474 if let Some(vis) = vis {
8475 self.complain_if_pub_macro(&vis.node, prev_span);
8480 // eat a matched-delimiter token tree:
8481 let (delim, tts) = self.expect_delimited_token_tree()?;
8482 if delim != MacDelimiter::Brace {
8483 self.expect(&token::Semi)?;
8486 Ok(Some(respan(lo.to(self.prev_span), Mac_ { path: pth, tts, delim })))
8492 fn collect_tokens<F, R>(&mut self, f: F) -> PResult<'a, (R, TokenStream)>
8493 where F: FnOnce(&mut Self) -> PResult<'a, R>
8495 // Record all tokens we parse when parsing this item.
8496 let mut tokens = Vec::new();
8497 let prev_collecting = match self.token_cursor.frame.last_token {
8498 LastToken::Collecting(ref mut list) => {
8499 Some(mem::replace(list, Vec::new()))
8501 LastToken::Was(ref mut last) => {
8502 tokens.extend(last.take());
8506 self.token_cursor.frame.last_token = LastToken::Collecting(tokens);
8507 let prev = self.token_cursor.stack.len();
8509 let last_token = if self.token_cursor.stack.len() == prev {
8510 &mut self.token_cursor.frame.last_token
8512 &mut self.token_cursor.stack[prev].last_token
8515 // Pull out the tokens that we've collected from the call to `f` above.
8516 let mut collected_tokens = match *last_token {
8517 LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()),
8518 LastToken::Was(_) => panic!("our vector went away?"),
8521 // If we're not at EOF our current token wasn't actually consumed by
8522 // `f`, but it'll still be in our list that we pulled out. In that case
8524 let extra_token = if self.token != token::Eof {
8525 collected_tokens.pop()
8530 // If we were previously collecting tokens, then this was a recursive
8531 // call. In that case we need to record all the tokens we collected in
8532 // our parent list as well. To do that we push a clone of our stream
8533 // onto the previous list.
8534 match prev_collecting {
8536 list.extend(collected_tokens.iter().cloned());
8537 list.extend(extra_token);
8538 *last_token = LastToken::Collecting(list);
8541 *last_token = LastToken::Was(extra_token);
8545 Ok((ret?, TokenStream::new(collected_tokens)))
8548 pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
8549 let attrs = self.parse_outer_attributes()?;
8550 self.parse_item_(attrs, true, false)
8554 fn is_import_coupler(&mut self) -> bool {
8555 self.check(&token::ModSep) &&
8556 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace) ||
8557 *t == token::BinOp(token::Star))
8560 /// Parses a `UseTree`.
8563 /// USE_TREE = [`::`] `*` |
8564 /// [`::`] `{` USE_TREE_LIST `}` |
8566 /// PATH `::` `{` USE_TREE_LIST `}` |
8567 /// PATH [`as` IDENT]
8569 fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
8572 let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
8573 let kind = if self.check(&token::OpenDelim(token::Brace)) ||
8574 self.check(&token::BinOp(token::Star)) ||
8575 self.is_import_coupler() {
8576 // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
8577 let mod_sep_ctxt = self.span.ctxt();
8578 if self.eat(&token::ModSep) {
8579 prefix.segments.push(
8580 PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt))
8584 if self.eat(&token::BinOp(token::Star)) {
8587 UseTreeKind::Nested(self.parse_use_tree_list()?)
8590 // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
8591 prefix = self.parse_path(PathStyle::Mod)?;
8593 if self.eat(&token::ModSep) {
8594 if self.eat(&token::BinOp(token::Star)) {
8597 UseTreeKind::Nested(self.parse_use_tree_list()?)
8600 UseTreeKind::Simple(self.parse_rename()?, ast::DUMMY_NODE_ID, ast::DUMMY_NODE_ID)
8604 Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
8607 /// Parses a `UseTreeKind::Nested(list)`.
8610 /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
8612 fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
8613 self.parse_unspanned_seq(&token::OpenDelim(token::Brace),
8614 &token::CloseDelim(token::Brace),
8615 SeqSep::trailing_allowed(token::Comma), |this| {
8616 Ok((this.parse_use_tree()?, ast::DUMMY_NODE_ID))
8620 fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
8621 if self.eat_keyword(keywords::As) {
8622 self.parse_ident_or_underscore().map(Some)
8628 /// Parses a source module as a crate. This is the main entry point for the parser.
8629 pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> {
8631 let krate = Ok(ast::Crate {
8632 attrs: self.parse_inner_attributes()?,
8633 module: self.parse_mod_items(&token::Eof, lo)?,
8634 span: lo.to(self.span),
8639 pub fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> {
8640 let ret = match self.token {
8641 token::Literal(token::Str_(s), suf) => (s, ast::StrStyle::Cooked, suf),
8642 token::Literal(token::StrRaw(s, n), suf) => (s, ast::StrStyle::Raw(n), suf),
8649 pub fn parse_str(&mut self) -> PResult<'a, (Symbol, StrStyle)> {
8650 match self.parse_optional_str() {
8651 Some((s, style, suf)) => {
8652 let sp = self.prev_span;
8653 self.expect_no_suffix(sp, "a string literal", suf);
8657 let msg = "expected string literal";
8658 let mut err = self.fatal(msg);
8659 err.span_label(self.span, msg);
8665 fn report_invalid_macro_expansion_item(&self) {
8666 self.struct_span_err(
8668 "macros that expand to items must be delimited with braces or followed by a semicolon",
8669 ).multipart_suggestion(
8670 "change the delimiters to curly braces",
8672 (self.prev_span.with_hi(self.prev_span.lo() + BytePos(1)), String::from(" {")),
8673 (self.prev_span.with_lo(self.prev_span.hi() - BytePos(1)), '}'.to_string()),
8675 Applicability::MaybeIncorrect,
8677 self.sess.source_map.next_point(self.prev_span),
8680 Applicability::MaybeIncorrect,
8684 /// Recover from `pub` keyword in places where it seems _reasonable_ but isn't valid.
8685 fn eat_bad_pub(&mut self) {
8686 if self.token.is_keyword(keywords::Pub) {
8687 match self.parse_visibility(false) {
8689 let mut err = self.diagnostic()
8690 .struct_span_err(vis.span, "unnecessary visibility qualifier");
8691 err.span_label(vis.span, "`pub` not permitted here");
8694 Err(mut err) => err.emit(),
8700 pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, handler: &errors::Handler) {
8701 for unmatched in unclosed_delims.iter() {
8702 let mut err = handler.struct_span_err(unmatched.found_span, &format!(
8703 "incorrect close delimiter: `{}`",
8704 pprust::token_to_string(&token::Token::CloseDelim(unmatched.found_delim)),
8706 err.span_label(unmatched.found_span, "incorrect close delimiter");
8707 if let Some(sp) = unmatched.candidate_span {
8708 err.span_label(sp, "close delimiter possibly meant for this");
8710 if let Some(sp) = unmatched.unclosed_span {
8711 err.span_label(sp, "un-closed delimiter");
8715 unclosed_delims.clear();