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::{BytePos, Span};
11 use rustc_span::symbol::{kw, sym};
13 use syntax::ast::{AttrStyle, AttrVec, Attribute, Mac, MacStmtStyle};
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 // Starts like a simple path, being careful to avoid contextual keywords,
56 // e.g., `union`, items with `crate` visibility, or `auto trait` items.
57 // We aim to parse an arbitrary path `a::b` but not something that starts like a path
58 // (1 token), but it fact not a path. Also, we avoid stealing syntax from `parse_item_`.
59 if self.token.is_path_start() && !self.token.is_qpath_start() && !self.is_path_start_item()
61 return self.parse_stmt_path_start(lo, attrs).map(Some);
64 if let Some(item) = self.parse_stmt_item(attrs.clone())? {
65 // FIXME: Bad copy of attrs
66 return Ok(Some(self.mk_stmt(lo.to(item.span), StmtKind::Item(P(item)))));
69 // Do not attempt to parse an expression if we're done here.
70 if self.token == token::Semi {
71 self.error_outer_attrs(&attrs);
73 let mut last_semi = lo;
74 while self.token == token::Semi {
75 last_semi = self.token.span;
78 // We are encoding a string of semicolons as an an empty tuple that spans
79 // the excess semicolons to preserve this info until the lint stage.
80 let kind = StmtKind::Semi(self.mk_expr(
82 ExprKind::Tup(Vec::new()),
85 return Ok(Some(self.mk_stmt(lo.to(last_semi), kind)));
88 if self.token == token::CloseDelim(token::Brace) {
89 self.error_outer_attrs(&attrs);
93 // Remainder are line-expr stmts.
94 let e = self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs.into()))?;
95 Ok(Some(self.mk_stmt(lo.to(e.span), StmtKind::Expr(e))))
98 fn parse_stmt_item(&mut self, attrs: Vec<Attribute>) -> PResult<'a, Option<ast::Item>> {
99 let old = mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
100 let item = self.parse_item_common(attrs.clone(), false, true, |_| true)?;
101 self.directory.ownership = old;
105 fn parse_stmt_path_start(&mut self, lo: Span, attrs: Vec<Attribute>) -> PResult<'a, Stmt> {
106 let path = self.parse_path(PathStyle::Expr)?;
108 if self.eat(&token::Not) {
109 return self.parse_stmt_mac(lo, attrs.into(), path);
112 let expr = if self.check(&token::OpenDelim(token::Brace)) {
113 self.parse_struct_expr(lo, path, AttrVec::new())?
115 let hi = self.prev_span;
116 self.mk_expr(lo.to(hi), ExprKind::Path(None, path), AttrVec::new())
119 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
120 let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
121 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
123 Ok(self.mk_stmt(lo.to(self.prev_span), StmtKind::Expr(expr)))
126 /// Parses a statement macro `mac!(args)` provided a `path` representing `mac`.
127 /// At this point, the `!` token after the path has already been eaten.
128 fn parse_stmt_mac(&mut self, lo: Span, attrs: AttrVec, path: ast::Path) -> PResult<'a, Stmt> {
129 let args = self.parse_mac_args()?;
130 let delim = args.delim();
131 let hi = self.prev_span;
134 if delim == token::Brace { MacStmtStyle::Braces } else { MacStmtStyle::NoBraces };
136 let mac = Mac { path, args, prior_type_ascription: self.last_type_ascription };
138 let kind = if delim == token::Brace || self.token == token::Semi || self.token == token::Eof
140 StmtKind::Mac(P((mac, style, attrs)))
142 // Since none of the above applied, this is an expression statement macro.
143 let e = self.mk_expr(lo.to(hi), ExprKind::Mac(mac), AttrVec::new());
144 let e = self.maybe_recover_from_bad_qpath(e, true)?;
145 let e = self.parse_dot_or_call_expr_with(e, lo, attrs)?;
146 let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
149 Ok(self.mk_stmt(lo.to(hi), kind))
152 /// Error on outer attributes in this context.
153 /// Also error if the previous token was a doc comment.
154 fn error_outer_attrs(&self, attrs: &[Attribute]) {
155 if !attrs.is_empty() {
156 if matches!(self.prev_token.kind, TokenKind::DocComment(..)) {
157 self.span_fatal_err(self.prev_span, Error::UselessDocComment).emit();
158 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
159 self.struct_span_err(self.token.span, "expected statement after outer attribute")
165 fn recover_stmt_local(
171 ) -> PResult<'a, Option<Stmt>> {
172 let stmt = self.parse_local_mk(lo, attrs)?;
173 self.struct_span_err(lo, "invalid variable declaration")
174 .span_suggestion(lo, msg, sugg.to_string(), Applicability::MachineApplicable)
179 fn parse_local_mk(&mut self, lo: Span, attrs: AttrVec) -> PResult<'a, Stmt> {
180 let local = self.parse_local(attrs.into())?;
181 Ok(self.mk_stmt(lo.to(self.prev_span), StmtKind::Local(local)))
184 /// Parses a local variable declaration.
185 fn parse_local(&mut self, attrs: AttrVec) -> PResult<'a, P<Local>> {
186 let lo = self.prev_span;
187 let pat = self.parse_top_pat(GateOr::Yes)?;
189 let (err, ty) = if self.eat(&token::Colon) {
190 // Save the state of the parser before parsing type normally, in case there is a `:`
191 // instead of an `=` typo.
192 let parser_snapshot_before_type = self.clone();
193 let colon_sp = self.prev_span;
194 match self.parse_ty() {
195 Ok(ty) => (None, Some(ty)),
197 // Rewind to before attempting to parse the type and continue parsing.
198 let parser_snapshot_after_type = self.clone();
199 mem::replace(self, parser_snapshot_before_type);
201 let snippet = self.span_to_snippet(pat.span).unwrap();
202 err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
203 (Some((parser_snapshot_after_type, colon_sp, err)), None)
209 let init = match (self.parse_initializer(err.is_some()), err) {
210 (Ok(init), None) => {
211 // init parsed, ty parsed
214 (Ok(init), Some((_, colon_sp, mut err))) => {
215 // init parsed, ty error
216 // Could parse the type as if it were the initializer, it is likely there was a
217 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
218 err.span_suggestion_short(
220 "use `=` if you meant to assign",
222 Applicability::MachineApplicable,
225 // As this was parsed successfully, continue as if the code has been fixed for the
226 // rest of the file. It will still fail due to the emitted error, but we avoid
230 (Err(mut init_err), Some((snapshot, _, ty_err))) => {
231 // init error, ty error
233 // Couldn't parse the type nor the initializer, only raise the type error and
234 // return to the parser state before parsing the type as the initializer.
235 // let x: <parse_error>;
236 mem::replace(self, snapshot);
239 (Err(err), None) => {
240 // init error, ty parsed
241 // Couldn't parse the initializer and we're not attempting to recover a failed
242 // parse of the type, return the error.
246 let hi = if self.token == token::Semi { self.token.span } else { self.prev_span };
247 Ok(P(ast::Local { ty, pat, init, id: DUMMY_NODE_ID, span: lo.to(hi), attrs }))
250 /// Parses the RHS of a local variable declaration (e.g., '= 14;').
251 fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
252 if self.eat(&token::Eq) {
253 Ok(Some(self.parse_expr()?))
255 Ok(Some(self.parse_expr()?))
261 /// Parses a block. No inner attributes are allowed.
262 pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
263 maybe_whole!(self, NtBlock, |x| x);
265 let lo = self.token.span;
267 if !self.eat(&token::OpenDelim(token::Brace)) {
268 return self.error_block_no_opening_brace();
271 self.parse_block_tail(lo, BlockCheckMode::Default)
274 fn error_block_no_opening_brace<T>(&mut self) -> PResult<'a, T> {
275 let sp = self.token.span;
276 let tok = super::token_descr(&self.token);
277 let mut e = self.struct_span_err(sp, &format!("expected `{{`, found {}", tok));
278 let do_not_suggest_help = self.token.is_keyword(kw::In) || self.token == token::Colon;
280 // Check to see if the user has written something like
285 // which is valid in other languages, but not Rust.
286 match self.parse_stmt_without_recovery() {
288 if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
289 || do_not_suggest_help
291 // If the next token is an open brace (e.g., `if a b {`), the place-
292 // inside-a-block suggestion would be more likely wrong than right.
293 e.span_label(sp, "expected `{`");
296 let stmt_span = if self.eat(&token::Semi) {
297 // Expand the span to include the semicolon.
298 stmt.span.with_hi(self.prev_span.hi())
302 if let Ok(snippet) = self.span_to_snippet(stmt_span) {
305 "try placing this code inside a block",
306 format!("{{ {} }}", snippet),
307 // Speculative; has been misleading in the past (#46836).
308 Applicability::MaybeIncorrect,
313 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
318 e.span_label(sp, "expected `{`");
322 /// Parses a block. Inner attributes are allowed.
323 pub(super) fn parse_inner_attrs_and_block(
325 ) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
326 maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
328 let lo = self.token.span;
329 self.expect(&token::OpenDelim(token::Brace))?;
330 Ok((self.parse_inner_attributes()?, self.parse_block_tail(lo, BlockCheckMode::Default)?))
333 /// Parses the rest of a block expression or function body.
334 /// Precondition: already parsed the '{'.
335 pub(super) fn parse_block_tail(
339 ) -> PResult<'a, P<Block>> {
340 let mut stmts = vec![];
341 while !self.eat(&token::CloseDelim(token::Brace)) {
342 if self.token == token::Eof {
345 let stmt = match self.parse_full_stmt() {
347 self.maybe_annotate_with_ascription(&mut err, false);
349 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
350 Some(self.mk_stmt_err(self.token.span))
354 if let Some(stmt) = stmt {
357 // Found only `;` or `}`.
361 Ok(self.mk_block(stmts, s, lo.to(self.prev_span)))
364 /// Parses a statement, including the trailing semicolon.
365 pub fn parse_full_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
366 // Skip looking for a trailing semicolon when we have an interpolated statement.
367 maybe_whole!(self, NtStmt, |x| Some(x));
369 let mut stmt = match self.parse_stmt_without_recovery()? {
371 None => return Ok(None),
374 let mut eat_semi = true;
376 StmtKind::Expr(ref expr) if self.token != token::Eof => {
377 // expression without semicolon
378 if classify::expr_requires_semi_to_be_stmt(expr) {
379 // Just check for errors and recover; do not eat semicolon yet.
381 self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
383 if let TokenKind::DocComment(..) = self.token.kind {
384 if let Ok(snippet) = self.span_to_snippet(self.token.span) {
385 let sp = self.token.span;
386 let marker = &snippet[..3];
387 let (comment_marker, doc_comment_marker) = marker.split_at(2);
390 sp.with_hi(sp.lo() + BytePos(marker.len() as u32)),
392 "add a space before `{}` to use a regular comment",
395 format!("{} {}", comment_marker, doc_comment_marker),
396 Applicability::MaybeIncorrect,
402 // Don't complain about type errors in body tail after parse error (#57383).
403 let sp = expr.span.to(self.prev_span);
404 stmt.kind = StmtKind::Expr(self.mk_expr_err(sp));
408 StmtKind::Local(..) => {
415 if eat_semi && self.eat(&token::Semi) {
416 stmt = stmt.add_trailing_semicolon();
418 stmt.span = stmt.span.to(self.prev_span);
422 pub(super) fn mk_block(&self, stmts: Vec<Stmt>, rules: BlockCheckMode, span: Span) -> P<Block> {
423 P(Block { stmts, id: DUMMY_NODE_ID, rules, span })
426 pub(super) fn mk_stmt(&self, span: Span, kind: StmtKind) -> Stmt {
427 Stmt { id: DUMMY_NODE_ID, kind, span }
430 fn mk_stmt_err(&self, span: Span) -> Stmt {
431 self.mk_stmt(span, StmtKind::Expr(self.mk_expr_err(span)))
434 pub(super) fn mk_block_err(&self, span: Span) -> P<Block> {
435 self.mk_block(vec![self.mk_stmt_err(span)], BlockCheckMode::Default, span)