1 use super::attr::DEFAULT_INNER_ATTR_FORBIDDEN;
2 use super::diagnostics::{AttemptLocalParseRecovery, Error};
3 use super::expr::LhsExpr;
4 use super::pat::RecoverComma;
5 use super::path::PathStyle;
6 use super::TrailingToken;
8 AttrWrapper, BlockMode, FnParseMode, ForceCollect, Parser, Restrictions, SemiColonMode,
10 use crate::maybe_whole;
13 use rustc_ast::ptr::P;
14 use rustc_ast::token::{self, Delimiter, TokenKind};
15 use rustc_ast::util::classify;
17 AstLike, AttrStyle, AttrVec, Attribute, LocalKind, MacCall, MacCallStmt, MacStmtStyle,
19 use rustc_ast::{Block, BlockCheckMode, Expr, ExprKind, Local, Stmt};
20 use rustc_ast::{StmtKind, DUMMY_NODE_ID};
21 use rustc_errors::{Applicability, DiagnosticBuilder, ErrorGuaranteed, PResult};
22 use rustc_span::source_map::{BytePos, Span};
23 use rustc_span::symbol::{kw, sym};
28 /// Parses a statement. This stops just before trailing semicolons on everything but items.
29 /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
30 // Public for rustfmt usage.
31 pub fn parse_stmt(&mut self, force_collect: ForceCollect) -> PResult<'a, Option<Stmt>> {
32 Ok(self.parse_stmt_without_recovery(false, force_collect).unwrap_or_else(|mut e| {
34 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
39 /// If `force_capture` is true, forces collection of tokens regardless of whether
40 /// or not we have attributes
41 crate fn parse_stmt_without_recovery(
44 force_collect: ForceCollect,
45 ) -> PResult<'a, Option<Stmt>> {
46 let attrs = self.parse_outer_attributes()?;
47 let lo = self.token.span;
49 // Don't use `maybe_whole` so that we have precise control
50 // over when we bump the parser
51 if let token::Interpolated(nt) = &self.token.kind && let token::NtStmt(stmt) = &**nt {
52 let mut stmt = stmt.clone();
54 stmt.visit_attrs(|stmt_attrs| {
55 attrs.prepend_to_nt_inner(stmt_attrs);
57 return Ok(Some(stmt.into_inner()));
60 Ok(Some(if self.token.is_keyword(kw::Let) {
61 self.parse_local_mk(lo, attrs, capture_semi, force_collect)?
62 } else if self.is_kw_followed_by_ident(kw::Mut) {
63 self.recover_stmt_local(lo, attrs, "missing keyword", "let mut")?
64 } else if self.is_kw_followed_by_ident(kw::Auto) {
65 self.bump(); // `auto`
66 let msg = "write `let` instead of `auto` to introduce a new variable";
67 self.recover_stmt_local(lo, attrs, msg, "let")?
68 } else if self.is_kw_followed_by_ident(sym::var) {
70 let msg = "write `let` instead of `var` to introduce a new variable";
71 self.recover_stmt_local(lo, attrs, msg, "let")?
72 } else if self.check_path() && !self.token.is_qpath_start() && !self.is_path_start_item() {
73 // We have avoided contextual keywords like `union`, items with `crate` visibility,
74 // or `auto trait` items. We aim to parse an arbitrary path `a::b` but not something
75 // that starts like a path (1 token), but it fact not a path.
76 // Also, we avoid stealing syntax from `parse_item_`.
77 if force_collect == ForceCollect::Yes {
78 self.collect_tokens_no_attrs(|this| this.parse_stmt_path_start(lo, attrs))
80 self.parse_stmt_path_start(lo, attrs)
82 } else if let Some(item) = self.parse_item_common(
86 FnParseMode { req_name: |_| true, req_body: true },
89 // FIXME: Bad copy of attrs
90 self.mk_stmt(lo.to(item.span), StmtKind::Item(P(item)))
91 } else if self.eat(&token::Semi) {
92 // Do not attempt to parse an expression if we're done here.
93 self.error_outer_attrs(&attrs.take_for_recovery());
94 self.mk_stmt(lo, StmtKind::Empty)
95 } else if self.token != token::CloseDelim(Delimiter::Brace) {
96 // Remainder are line-expr stmts.
97 let e = if force_collect == ForceCollect::Yes {
98 self.collect_tokens_no_attrs(|this| {
99 this.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs))
102 self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs))
104 if matches!(e.kind, ExprKind::Assign(..)) && self.eat_keyword(kw::Else) {
105 let bl = self.parse_block()?;
106 // Destructuring assignment ... else.
107 // This is not allowed, but point it out in a nice way.
108 let mut err = self.struct_span_err(
110 "<assignment> ... else { ... } is not allowed",
114 self.mk_stmt(lo.to(e.span), StmtKind::Expr(e))
116 self.error_outer_attrs(&attrs.take_for_recovery());
121 fn parse_stmt_path_start(&mut self, lo: Span, attrs: AttrWrapper) -> PResult<'a, Stmt> {
122 let stmt = self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
123 let path = this.parse_path(PathStyle::Expr)?;
125 if this.eat(&token::Not) {
126 let stmt_mac = this.parse_stmt_mac(lo, attrs.into(), path)?;
127 if this.token == token::Semi {
128 return Ok((stmt_mac, TrailingToken::Semi));
130 return Ok((stmt_mac, TrailingToken::None));
134 let expr = if this.eat(&token::OpenDelim(Delimiter::Brace)) {
135 this.parse_struct_expr(None, path, AttrVec::new(), true)?
137 let hi = this.prev_token.span;
138 this.mk_expr(lo.to(hi), ExprKind::Path(None, path), AttrVec::new())
141 let expr = this.with_res(Restrictions::STMT_EXPR, |this| {
142 this.parse_dot_or_call_expr_with(expr, lo, attrs)
144 // `DUMMY_SP` will get overwritten later in this function
145 Ok((this.mk_stmt(rustc_span::DUMMY_SP, StmtKind::Expr(expr)), TrailingToken::None))
148 if let StmtKind::Expr(expr) = stmt.kind {
149 // Perform this outside of the `collect_tokens_trailing_token` closure,
150 // since our outer attributes do not apply to this part of the expression
151 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
152 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
154 Ok(self.mk_stmt(lo.to(self.prev_token.span), StmtKind::Expr(expr)))
160 /// Parses a statement macro `mac!(args)` provided a `path` representing `mac`.
161 /// At this point, the `!` token after the path has already been eaten.
162 fn parse_stmt_mac(&mut self, lo: Span, attrs: AttrVec, path: ast::Path) -> PResult<'a, Stmt> {
163 let args = self.parse_mac_args()?;
164 let delim = args.delim();
165 let hi = self.prev_token.span;
167 let style = match delim {
168 Some(Delimiter::Brace) => MacStmtStyle::Braces,
169 Some(_) => MacStmtStyle::NoBraces,
170 None => unreachable!(),
173 let mac = MacCall { path, args, prior_type_ascription: self.last_type_ascription };
175 let kind = if (style == MacStmtStyle::Braces
176 && self.token != token::Dot
177 && self.token != token::Question)
178 || self.token == token::Semi
179 || self.token == token::Eof
181 StmtKind::MacCall(P(MacCallStmt { mac, style, attrs, tokens: None }))
183 // Since none of the above applied, this is an expression statement macro.
184 let e = self.mk_expr(lo.to(hi), ExprKind::MacCall(mac), AttrVec::new());
185 let e = self.maybe_recover_from_bad_qpath(e, true)?;
186 let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
187 let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
190 Ok(self.mk_stmt(lo.to(hi), kind))
193 /// Error on outer attributes in this context.
194 /// Also error if the previous token was a doc comment.
195 fn error_outer_attrs(&self, attrs: &[Attribute]) {
196 if let [.., last] = attrs {
197 if last.is_doc_comment() {
198 self.span_err(last.span, Error::UselessDocComment).emit();
199 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
200 self.struct_span_err(last.span, "expected statement after outer attribute").emit();
205 fn recover_stmt_local(
211 ) -> PResult<'a, Stmt> {
212 let stmt = self.recover_local_after_let(lo, attrs)?;
213 self.struct_span_err(lo, "invalid variable declaration")
214 .span_suggestion(lo, msg, sugg.to_string(), Applicability::MachineApplicable)
224 force_collect: ForceCollect,
225 ) -> PResult<'a, Stmt> {
226 self.collect_tokens_trailing_token(attrs, force_collect, |this, attrs| {
227 this.expect_keyword(kw::Let)?;
228 let local = this.parse_local(attrs.into())?;
229 let trailing = if capture_semi && this.token.kind == token::Semi {
234 Ok((this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Local(local)), trailing))
238 fn recover_local_after_let(&mut self, lo: Span, attrs: AttrWrapper) -> PResult<'a, Stmt> {
239 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
240 let local = this.parse_local(attrs.into())?;
241 // FIXME - maybe capture semicolon in recovery?
243 this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Local(local)),
249 /// Parses a local variable declaration.
250 fn parse_local(&mut self, attrs: AttrVec) -> PResult<'a, P<Local>> {
251 let lo = self.prev_token.span;
252 let (pat, colon) = self.parse_pat_before_ty(None, RecoverComma::Yes, "`let` bindings")?;
254 let (err, ty) = if colon {
255 // Save the state of the parser before parsing type normally, in case there is a `:`
256 // instead of an `=` typo.
257 let parser_snapshot_before_type = self.clone();
258 let colon_sp = self.prev_token.span;
259 match self.parse_ty() {
260 Ok(ty) => (None, Some(ty)),
262 if let Ok(snip) = self.span_to_snippet(pat.span) {
263 err.span_label(pat.span, format!("while parsing the type for `{}`", snip));
265 let err = if self.check(&token::Eq) {
269 // Rewind to before attempting to parse the type and continue parsing.
270 let parser_snapshot_after_type =
271 mem::replace(self, parser_snapshot_before_type);
272 Some((parser_snapshot_after_type, colon_sp, err))
280 let init = match (self.parse_initializer(err.is_some()), err) {
281 (Ok(init), None) => {
282 // init parsed, ty parsed
285 (Ok(init), Some((_, colon_sp, mut err))) => {
286 // init parsed, ty error
287 // Could parse the type as if it were the initializer, it is likely there was a
288 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
289 err.span_suggestion_short(
291 "use `=` if you meant to assign",
293 Applicability::MachineApplicable,
296 // As this was parsed successfully, continue as if the code has been fixed for the
297 // rest of the file. It will still fail due to the emitted error, but we avoid
301 (Err(init_err), Some((snapshot, _, ty_err))) => {
302 // init error, ty error
304 // Couldn't parse the type nor the initializer, only raise the type error and
305 // return to the parser state before parsing the type as the initializer.
306 // let x: <parse_error>;
310 (Err(err), None) => {
311 // init error, ty parsed
312 // Couldn't parse the initializer and we're not attempting to recover a failed
313 // parse of the type, return the error.
317 let kind = match init {
318 None => LocalKind::Decl,
320 if self.eat_keyword(kw::Else) {
321 if self.token.is_keyword(kw::If) {
322 // `let...else if`. Emit the same error that `parse_block()` would,
323 // but explicitly point out that this pattern is not allowed.
324 let msg = "conditional `else if` is not supported for `let...else`";
325 return Err(self.error_block_no_opening_brace_msg(msg));
327 let els = self.parse_block()?;
328 self.check_let_else_init_bool_expr(&init);
329 self.check_let_else_init_trailing_brace(&init);
330 LocalKind::InitElse(init, els)
332 LocalKind::Init(init)
336 let hi = if self.token == token::Semi { self.token.span } else { self.prev_token.span };
337 Ok(P(ast::Local { ty, pat, kind, id: DUMMY_NODE_ID, span: lo.to(hi), attrs, tokens: None }))
340 fn check_let_else_init_bool_expr(&self, init: &ast::Expr) {
341 if let ast::ExprKind::Binary(op, ..) = init.kind {
344 (init.span.shrink_to_lo(), "(".to_string()),
345 (init.span.shrink_to_hi(), ")".to_string()),
347 self.struct_span_err(
350 "a `{}` expression cannot be directly assigned in `let...else`",
354 .multipart_suggestion(
355 "wrap the expression in parentheses",
357 Applicability::MachineApplicable,
364 fn check_let_else_init_trailing_brace(&self, init: &ast::Expr) {
365 if let Some(trailing) = classify::expr_trailing_brace(init) {
366 let err_span = trailing.span.with_lo(trailing.span.hi() - BytePos(1));
368 (trailing.span.shrink_to_lo(), "(".to_string()),
369 (trailing.span.shrink_to_hi(), ")".to_string()),
371 self.struct_span_err(
373 "right curly brace `}` before `else` in a `let...else` statement not allowed",
375 .multipart_suggestion(
376 "try wrapping the expression in parentheses",
378 Applicability::MachineApplicable,
384 /// Parses the RHS of a local variable declaration (e.g., `= 14;`).
385 fn parse_initializer(&mut self, eq_optional: bool) -> PResult<'a, Option<P<Expr>>> {
386 let eq_consumed = match self.token.kind {
387 token::BinOpEq(..) => {
388 // Recover `let x <op>= 1` as `let x = 1`
389 self.struct_span_err(
391 "can't reassign to an uninitialized variable",
393 .span_suggestion_short(
395 "initialize the variable",
397 Applicability::MaybeIncorrect,
399 .help("if you meant to overwrite, remove the `let` binding")
404 _ => self.eat(&token::Eq),
407 Ok(if eq_consumed || eq_optional { Some(self.parse_expr()?) } else { None })
410 /// Parses a block. No inner attributes are allowed.
411 pub(super) fn parse_block(&mut self) -> PResult<'a, P<Block>> {
412 let (attrs, block) = self.parse_inner_attrs_and_block()?;
413 if let [.., last] = &*attrs {
414 self.error_on_forbidden_inner_attr(last.span, DEFAULT_INNER_ATTR_FORBIDDEN);
419 fn error_block_no_opening_brace_msg(
422 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
423 let sp = self.token.span;
424 let mut e = self.struct_span_err(sp, msg);
425 let do_not_suggest_help = self.token.is_keyword(kw::In) || self.token == token::Colon;
427 // Check to see if the user has written something like
432 // which is valid in other languages, but not Rust.
433 match self.parse_stmt_without_recovery(false, ForceCollect::No) {
434 // If the next token is an open brace (e.g., `if a b {`), the place-
435 // inside-a-block suggestion would be more likely wrong than right.
437 if self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Brace))
438 || do_not_suggest_help => {}
439 // Do not suggest `if foo println!("") {;}` (as would be seen in test for #46836).
440 Ok(Some(Stmt { kind: StmtKind::Empty, .. })) => {}
442 let stmt_own_line = self.sess.source_map().is_line_before_span_empty(sp);
443 let stmt_span = if stmt_own_line && self.eat(&token::Semi) {
444 // Expand the span to include the semicolon.
445 stmt.span.with_hi(self.prev_token.span.hi())
449 e.multipart_suggestion(
450 "try placing this code inside a block",
452 (stmt_span.shrink_to_lo(), "{ ".to_string()),
453 (stmt_span.shrink_to_hi(), " }".to_string()),
455 // Speculative; has been misleading in the past (#46836).
456 Applicability::MaybeIncorrect,
460 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
465 e.span_label(sp, "expected `{`");
469 fn error_block_no_opening_brace<T>(&mut self) -> PResult<'a, T> {
470 let tok = super::token_descr(&self.token);
471 let msg = format!("expected `{{`, found {}", tok);
472 Err(self.error_block_no_opening_brace_msg(&msg))
475 /// Parses a block. Inner attributes are allowed.
476 pub(super) fn parse_inner_attrs_and_block(
478 ) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
479 self.parse_block_common(self.token.span, BlockCheckMode::Default)
482 /// Parses a block. Inner attributes are allowed.
483 pub(super) fn parse_block_common(
486 blk_mode: BlockCheckMode,
487 ) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
488 maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
490 self.maybe_recover_unexpected_block_label();
491 if !self.eat(&token::OpenDelim(Delimiter::Brace)) {
492 return self.error_block_no_opening_brace();
495 let attrs = self.parse_inner_attributes()?;
496 let tail = match self.maybe_suggest_struct_literal(lo, blk_mode) {
498 None => self.parse_block_tail(lo, blk_mode, AttemptLocalParseRecovery::Yes)?,
503 /// Parses the rest of a block expression or function body.
504 /// Precondition: already parsed the '{'.
505 crate fn parse_block_tail(
509 recover: AttemptLocalParseRecovery,
510 ) -> PResult<'a, P<Block>> {
511 let mut stmts = vec![];
512 while !self.eat(&token::CloseDelim(Delimiter::Brace)) {
513 if self.token == token::Eof {
516 let stmt = match self.parse_full_stmt(recover) {
517 Err(mut err) if recover.yes() => {
518 self.maybe_annotate_with_ascription(&mut err, false);
520 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
521 Some(self.mk_stmt_err(self.token.span))
524 Err(err) => return Err(err),
526 if let Some(stmt) = stmt {
529 // Found only `;` or `}`.
533 Ok(self.mk_block(stmts, s, lo.to(self.prev_token.span)))
536 /// Parses a statement, including the trailing semicolon.
537 pub fn parse_full_stmt(
539 recover: AttemptLocalParseRecovery,
540 ) -> PResult<'a, Option<Stmt>> {
541 // Skip looking for a trailing semicolon when we have an interpolated statement.
542 maybe_whole!(self, NtStmt, |x| Some(x.into_inner()));
544 let Some(mut stmt) = self.parse_stmt_without_recovery(true, ForceCollect::No)? else {
548 let mut eat_semi = true;
550 // Expression without semicolon.
551 StmtKind::Expr(ref mut expr)
552 if self.token != token::Eof && classify::expr_requires_semi_to_be_stmt(expr) =>
554 // Just check for errors and recover; do not eat semicolon yet.
556 self.expect_one_of(&[], &[token::Semi, token::CloseDelim(Delimiter::Brace)])
558 if let TokenKind::DocComment(..) = self.token.kind {
559 if let Ok(snippet) = self.span_to_snippet(self.token.span) {
560 let sp = self.token.span;
561 let marker = &snippet[..3];
562 let (comment_marker, doc_comment_marker) = marker.split_at(2);
565 sp.with_hi(sp.lo() + BytePos(marker.len() as u32)),
567 "add a space before `{}` to use a regular comment",
570 format!("{} {}", comment_marker, doc_comment_marker),
571 Applicability::MaybeIncorrect,
576 self.check_mistyped_turbofish_with_multiple_type_params(e, expr)
584 // Don't complain about type errors in body tail after parse error (#57383).
585 let sp = expr.span.to(self.prev_token.span);
586 *expr = self.mk_expr_err(sp);
589 StmtKind::Expr(_) | StmtKind::MacCall(_) => {}
590 StmtKind::Local(ref mut local) if let Err(e) = self.expect_semi() => {
591 // We might be at the `,` in `let x = foo<bar, baz>;`. Try to recover.
592 match &mut local.kind {
593 LocalKind::Init(expr) | LocalKind::InitElse(expr, _) => {
594 self.check_mistyped_turbofish_with_multiple_type_params(e, expr)?;
595 // We found `foo<bar, baz>`, have we fully recovered?
598 LocalKind::Decl => return Err(e),
602 StmtKind::Empty | StmtKind::Item(_) | StmtKind::Local(_) | StmtKind::Semi(_) => eat_semi = false,
605 if eat_semi && self.eat(&token::Semi) {
606 stmt = stmt.add_trailing_semicolon();
608 stmt.span = stmt.span.to(self.prev_token.span);
612 pub(super) fn mk_block(&self, stmts: Vec<Stmt>, rules: BlockCheckMode, span: Span) -> P<Block> {
619 could_be_bare_literal: false,
623 pub(super) fn mk_stmt(&self, span: Span, kind: StmtKind) -> Stmt {
624 Stmt { id: DUMMY_NODE_ID, kind, span }
627 pub(super) fn mk_stmt_err(&self, span: Span) -> Stmt {
628 self.mk_stmt(span, StmtKind::Expr(self.mk_expr_err(span)))
631 pub(super) fn mk_block_err(&self, span: Span) -> P<Block> {
632 self.mk_block(vec![self.mk_stmt_err(span)], BlockCheckMode::Default, span)