1 use super::diagnostics::Error;
2 use super::expr::LhsExpr;
3 use super::pat::GateOr;
4 use super::path::PathStyle;
5 use super::{BlockMode, Parser, Restrictions, SemiColonMode};
6 use crate::maybe_whole;
7 use crate::DirectoryOwnership;
9 use rustc_errors::{Applicability, PResult};
10 use rustc_span::source_map::{respan, BytePos, Span};
11 use rustc_span::symbol::{kw, sym, Symbol};
13 use syntax::ast::{AttrStyle, AttrVec, Attribute, Mac, MacStmtStyle, VisibilityKind};
14 use syntax::ast::{Block, BlockCheckMode, Expr, ExprKind, Local, Stmt, StmtKind, DUMMY_NODE_ID};
16 use syntax::token::{self, TokenKind};
17 use syntax::util::classify;
22 /// Parses a statement. This stops just before trailing semicolons on everything but items.
23 /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
24 pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
25 Ok(self.parse_stmt_without_recovery().unwrap_or_else(|mut e| {
27 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
32 fn parse_stmt_without_recovery(&mut self) -> PResult<'a, Option<Stmt>> {
33 maybe_whole!(self, NtStmt, |x| Some(x));
35 let attrs = self.parse_outer_attributes()?;
36 let lo = self.token.span;
38 if self.eat_keyword(kw::Let) {
39 return self.parse_local_mk(lo, attrs.into()).map(Some);
41 if self.is_kw_followed_by_ident(kw::Mut) {
42 return self.recover_stmt_local(lo, attrs.into(), "missing keyword", "let mut");
44 if self.is_kw_followed_by_ident(kw::Auto) {
45 self.bump(); // `auto`
46 let msg = "write `let` instead of `auto` to introduce a new variable";
47 return self.recover_stmt_local(lo, attrs.into(), msg, "let");
49 if self.is_kw_followed_by_ident(sym::var) {
51 let msg = "write `let` instead of `var` to introduce a new variable";
52 return self.recover_stmt_local(lo, attrs.into(), msg, "let");
55 let mac_vis = respan(lo, VisibilityKind::Inherited);
56 if let Some(macro_def) = self.eat_macro_def(&attrs, &mac_vis, lo)? {
57 return Ok(Some(self.mk_stmt(lo.to(self.prev_span), StmtKind::Item(macro_def))));
60 // Starts like a simple path, being careful to avoid contextual keywords
61 // such as a union items, item with `crate` visibility or auto trait items.
62 // Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
63 // like a path (1 token), but it fact not a path.
64 if self.token.is_path_start()
65 && !self.token.is_qpath_start()
66 && !self.is_union_item() // `union::b::c` - path, `union U { ... }` - not a path.
67 && !self.is_crate_vis() // `crate::b::c` - path, `crate struct S;` - not a path.
68 && !self.is_auto_trait_item()
69 && !self.is_async_fn()
71 let path = self.parse_path(PathStyle::Expr)?;
73 if self.eat(&token::Not) {
74 return self.parse_stmt_mac(lo, attrs.into(), path);
77 let expr = if self.check(&token::OpenDelim(token::Brace)) {
78 self.parse_struct_expr(lo, path, AttrVec::new())?
80 let hi = self.prev_span;
81 self.mk_expr(lo.to(hi), ExprKind::Path(None, path), AttrVec::new())
84 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
85 let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
86 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
88 return Ok(Some(self.mk_stmt(lo.to(self.prev_span), StmtKind::Expr(expr))));
91 // FIXME: Bad copy of attrs
92 let old_directory_ownership =
93 mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
94 let item = self.parse_item_(attrs.clone(), false, true)?;
95 self.directory.ownership = old_directory_ownership;
97 if let Some(item) = item {
98 return Ok(Some(self.mk_stmt(lo.to(item.span), StmtKind::Item(item))));
101 // Do not attempt to parse an expression if we're done here.
102 if self.token == token::Semi {
103 self.error_outer_attrs(&attrs);
105 let mut last_semi = lo;
106 while self.token == token::Semi {
107 last_semi = self.token.span;
110 // We are encoding a string of semicolons as an an empty tuple that spans
111 // the excess semicolons to preserve this info until the lint stage.
112 let kind = StmtKind::Semi(self.mk_expr(
114 ExprKind::Tup(Vec::new()),
117 return Ok(Some(self.mk_stmt(lo.to(last_semi), kind)));
120 if self.token == token::CloseDelim(token::Brace) {
121 self.error_outer_attrs(&attrs);
125 // Remainder are line-expr stmts.
126 let e = self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs.into()))?;
127 Ok(Some(self.mk_stmt(lo.to(e.span), StmtKind::Expr(e))))
130 /// Parses a statement macro `mac!(args)` provided a `path` representing `mac`.
131 /// At this point, the `!` token after the path has already been eaten.
137 ) -> PResult<'a, Option<Stmt>> {
138 let args = self.parse_mac_args()?;
139 let delim = args.delim();
140 let hi = self.prev_span;
143 if delim == token::Brace { MacStmtStyle::Braces } else { MacStmtStyle::NoBraces };
145 let mac = Mac { path, args, prior_type_ascription: self.last_type_ascription };
147 let kind = if delim == token::Brace || self.token == token::Semi || self.token == token::Eof
149 StmtKind::Mac(P((mac, style, attrs)))
151 // Since none of the above applied, this is an expression statement macro.
152 let e = self.mk_expr(lo.to(hi), ExprKind::Mac(mac), AttrVec::new());
153 let e = self.maybe_recover_from_bad_qpath(e, true)?;
154 let e = self.parse_dot_or_call_expr_with(e, lo, attrs)?;
155 let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
158 Ok(Some(self.mk_stmt(lo.to(hi), kind)))
161 /// Error on outer attributes in this context.
162 /// Also error if the previous token was a doc comment.
163 fn error_outer_attrs(&self, attrs: &[Attribute]) {
164 if !attrs.is_empty() {
165 if matches!(self.prev_token.kind, TokenKind::DocComment(..)) {
166 self.span_fatal_err(self.prev_span, Error::UselessDocComment).emit();
167 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
168 self.struct_span_err(self.token.span, "expected statement after outer attribute")
174 pub(super) fn is_kw_followed_by_ident(&self, kw: Symbol) -> bool {
175 self.token.is_keyword(kw) && self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
178 fn recover_stmt_local(
184 ) -> PResult<'a, Option<Stmt>> {
185 let stmt = self.parse_local_mk(lo, attrs)?;
186 self.struct_span_err(lo, "invalid variable declaration")
187 .span_suggestion(lo, msg, sugg.to_string(), Applicability::MachineApplicable)
192 fn parse_local_mk(&mut self, lo: Span, attrs: AttrVec) -> PResult<'a, Stmt> {
193 let local = self.parse_local(attrs.into())?;
194 Ok(self.mk_stmt(lo.to(self.prev_span), StmtKind::Local(local)))
197 /// Parses a local variable declaration.
198 fn parse_local(&mut self, attrs: AttrVec) -> PResult<'a, P<Local>> {
199 let lo = self.prev_span;
200 let pat = self.parse_top_pat(GateOr::Yes)?;
202 let (err, ty) = if self.eat(&token::Colon) {
203 // Save the state of the parser before parsing type normally, in case there is a `:`
204 // instead of an `=` typo.
205 let parser_snapshot_before_type = self.clone();
206 let colon_sp = self.prev_span;
207 match self.parse_ty() {
208 Ok(ty) => (None, Some(ty)),
210 // Rewind to before attempting to parse the type and continue parsing.
211 let parser_snapshot_after_type = self.clone();
212 mem::replace(self, parser_snapshot_before_type);
214 let snippet = self.span_to_snippet(pat.span).unwrap();
215 err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
216 (Some((parser_snapshot_after_type, colon_sp, err)), None)
222 let init = match (self.parse_initializer(err.is_some()), err) {
223 (Ok(init), None) => {
224 // init parsed, ty parsed
227 (Ok(init), Some((_, colon_sp, mut err))) => {
228 // init parsed, ty error
229 // Could parse the type as if it were the initializer, it is likely there was a
230 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
231 err.span_suggestion_short(
233 "use `=` if you meant to assign",
235 Applicability::MachineApplicable,
238 // As this was parsed successfully, continue as if the code has been fixed for the
239 // rest of the file. It will still fail due to the emitted error, but we avoid
243 (Err(mut init_err), Some((snapshot, _, ty_err))) => {
244 // init error, ty error
246 // Couldn't parse the type nor the initializer, only raise the type error and
247 // return to the parser state before parsing the type as the initializer.
248 // let x: <parse_error>;
249 mem::replace(self, snapshot);
252 (Err(err), None) => {
253 // init error, ty parsed
254 // Couldn't parse the initializer and we're not attempting to recover a failed
255 // parse of the type, return the error.
259 let hi = if self.token == token::Semi { self.token.span } else { self.prev_span };
260 Ok(P(ast::Local { ty, pat, init, id: DUMMY_NODE_ID, span: lo.to(hi), attrs }))
263 /// Parses the RHS of a local variable declaration (e.g., '= 14;').
264 fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
265 if self.eat(&token::Eq) {
266 Ok(Some(self.parse_expr()?))
268 Ok(Some(self.parse_expr()?))
274 fn is_auto_trait_item(&self) -> bool {
276 (self.token.is_keyword(kw::Auto) &&
277 self.is_keyword_ahead(1, &[kw::Trait]))
278 || // unsafe auto trait
279 (self.token.is_keyword(kw::Unsafe) &&
280 self.is_keyword_ahead(1, &[kw::Auto]) &&
281 self.is_keyword_ahead(2, &[kw::Trait]))
284 /// Parses a block. No inner attributes are allowed.
285 pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
286 maybe_whole!(self, NtBlock, |x| x);
288 let lo = self.token.span;
290 if !self.eat(&token::OpenDelim(token::Brace)) {
291 return self.error_block_no_opening_brace();
294 self.parse_block_tail(lo, BlockCheckMode::Default)
297 fn error_block_no_opening_brace<T>(&mut self) -> PResult<'a, T> {
298 let sp = self.token.span;
299 let tok = super::token_descr(&self.token);
300 let mut e = self.struct_span_err(sp, &format!("expected `{{`, found {}", tok));
301 let do_not_suggest_help = self.token.is_keyword(kw::In) || self.token == token::Colon;
303 // Check to see if the user has written something like
308 // which is valid in other languages, but not Rust.
309 match self.parse_stmt_without_recovery() {
311 if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
312 || do_not_suggest_help
314 // If the next token is an open brace (e.g., `if a b {`), the place-
315 // inside-a-block suggestion would be more likely wrong than right.
316 e.span_label(sp, "expected `{`");
319 let stmt_span = if self.eat(&token::Semi) {
320 // Expand the span to include the semicolon.
321 stmt.span.with_hi(self.prev_span.hi())
325 if let Ok(snippet) = self.span_to_snippet(stmt_span) {
328 "try placing this code inside a block",
329 format!("{{ {} }}", snippet),
330 // Speculative; has been misleading in the past (#46836).
331 Applicability::MaybeIncorrect,
336 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
341 e.span_label(sp, "expected `{`");
345 /// Parses a block. Inner attributes are allowed.
346 pub(super) fn parse_inner_attrs_and_block(
348 ) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
349 maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
351 let lo = self.token.span;
352 self.expect(&token::OpenDelim(token::Brace))?;
353 Ok((self.parse_inner_attributes()?, self.parse_block_tail(lo, BlockCheckMode::Default)?))
356 /// Parses the rest of a block expression or function body.
357 /// Precondition: already parsed the '{'.
358 pub(super) fn parse_block_tail(
362 ) -> PResult<'a, P<Block>> {
363 let mut stmts = vec![];
364 while !self.eat(&token::CloseDelim(token::Brace)) {
365 if self.token == token::Eof {
368 let stmt = match self.parse_full_stmt() {
370 self.maybe_annotate_with_ascription(&mut err, false);
372 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
373 Some(self.mk_stmt_err(self.token.span))
377 if let Some(stmt) = stmt {
380 // Found only `;` or `}`.
384 Ok(self.mk_block(stmts, s, lo.to(self.prev_span)))
387 /// Parses a statement, including the trailing semicolon.
388 pub fn parse_full_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
389 // Skip looking for a trailing semicolon when we have an interpolated statement.
390 maybe_whole!(self, NtStmt, |x| Some(x));
392 let mut stmt = match self.parse_stmt_without_recovery()? {
394 None => return Ok(None),
397 let mut eat_semi = true;
399 StmtKind::Expr(ref expr) if self.token != token::Eof => {
400 // expression without semicolon
401 if classify::expr_requires_semi_to_be_stmt(expr) {
402 // Just check for errors and recover; do not eat semicolon yet.
404 self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
406 if let TokenKind::DocComment(..) = self.token.kind {
407 if let Ok(snippet) = self.span_to_snippet(self.token.span) {
408 let sp = self.token.span;
409 let marker = &snippet[..3];
410 let (comment_marker, doc_comment_marker) = marker.split_at(2);
413 sp.with_hi(sp.lo() + BytePos(marker.len() as u32)),
415 "add a space before `{}` to use a regular comment",
418 format!("{} {}", comment_marker, doc_comment_marker),
419 Applicability::MaybeIncorrect,
425 // Don't complain about type errors in body tail after parse error (#57383).
426 let sp = expr.span.to(self.prev_span);
427 stmt.kind = StmtKind::Expr(self.mk_expr_err(sp));
431 StmtKind::Local(..) => {
438 if eat_semi && self.eat(&token::Semi) {
439 stmt = stmt.add_trailing_semicolon();
441 stmt.span = stmt.span.to(self.prev_span);
445 pub(super) fn mk_block(&self, stmts: Vec<Stmt>, rules: BlockCheckMode, span: Span) -> P<Block> {
446 P(Block { stmts, id: DUMMY_NODE_ID, rules, span })
449 pub(super) fn mk_stmt(&self, span: Span, kind: StmtKind) -> Stmt {
450 Stmt { id: DUMMY_NODE_ID, kind, span }
453 fn mk_stmt_err(&self, span: Span) -> Stmt {
454 self.mk_stmt(span, StmtKind::Expr(self.mk_expr_err(span)))
457 pub(super) fn mk_block_err(&self, span: Span) -> P<Block> {
458 self.mk_block(vec![self.mk_stmt_err(span)], BlockCheckMode::Default, span)