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(true).unwrap_or_else(|mut e| {
27 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
32 fn parse_stmt_without_recovery(
34 macro_legacy_warnings: bool,
35 ) -> PResult<'a, Option<Stmt>> {
36 maybe_whole!(self, NtStmt, |x| Some(x));
38 let attrs = self.parse_outer_attributes()?;
39 let lo = self.token.span;
41 if self.eat_keyword(kw::Let) {
42 return self.parse_local_mk(lo, attrs.into()).map(Some);
44 if self.is_kw_followed_by_ident(kw::Mut) {
45 return self.recover_stmt_local(lo, attrs.into(), "missing keyword", "let mut");
47 if self.is_kw_followed_by_ident(kw::Auto) {
48 self.bump(); // `auto`
49 let msg = "write `let` instead of `auto` to introduce a new variable";
50 return self.recover_stmt_local(lo, attrs.into(), msg, "let");
52 if self.is_kw_followed_by_ident(sym::var) {
54 let msg = "write `let` instead of `var` to introduce a new variable";
55 return self.recover_stmt_local(lo, attrs.into(), msg, "let");
58 // Starts like a simple path, being careful to avoid contextual keywords,
59 // e.g., `union`, items with `crate` visibility, or `auto trait` items.
60 // We aim to parse an arbitrary path `a::b` but not something that starts like a path
61 // (1 token), but it fact not a path. Also, we avoid stealing syntax from `parse_item_`.
62 if self.token.is_path_start() && !self.token.is_qpath_start() && !self.is_path_start_item()
64 let path = self.parse_path(PathStyle::Expr)?;
66 if self.eat(&token::Not) {
67 return self.parse_stmt_mac(lo, attrs.into(), path, macro_legacy_warnings);
70 let expr = if self.check(&token::OpenDelim(token::Brace)) {
71 self.parse_struct_expr(lo, path, AttrVec::new())?
73 let hi = self.prev_span;
74 self.mk_expr(lo.to(hi), ExprKind::Path(None, path), AttrVec::new())
77 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
78 let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
79 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
81 return Ok(Some(self.mk_stmt(lo.to(self.prev_span), StmtKind::Expr(expr))));
84 // FIXME: Bad copy of attrs
85 let old_directory_ownership =
86 mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
87 let item = self.parse_item_(attrs.clone(), false, true)?;
88 self.directory.ownership = old_directory_ownership;
90 if let Some(item) = item {
91 return Ok(Some(self.mk_stmt(lo.to(item.span), StmtKind::Item(item))));
94 // Do not attempt to parse an expression if we're done here.
95 if self.token == token::Semi {
96 self.error_outer_attrs(&attrs);
98 let mut last_semi = lo;
99 while self.token == token::Semi {
100 last_semi = self.token.span;
103 // We are encoding a string of semicolons as an an empty tuple that spans
104 // the excess semicolons to preserve this info until the lint stage.
105 let kind = StmtKind::Semi(self.mk_expr(
107 ExprKind::Tup(Vec::new()),
110 return Ok(Some(self.mk_stmt(lo.to(last_semi), kind)));
113 if self.token == token::CloseDelim(token::Brace) {
114 self.error_outer_attrs(&attrs);
118 // Remainder are line-expr stmts.
119 let e = self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs.into()))?;
120 Ok(Some(self.mk_stmt(lo.to(e.span), StmtKind::Expr(e))))
123 /// Parses a statement macro `mac!(args)` provided a `path` representing `mac`.
124 /// At this point, the `!` token after the path has already been eaten.
130 legacy_warnings: bool,
131 ) -> PResult<'a, Option<Stmt>> {
132 let args = self.parse_mac_args()?;
133 let delim = args.delim();
134 let hi = self.prev_span;
137 if delim == token::Brace { MacStmtStyle::Braces } else { MacStmtStyle::NoBraces };
139 let mac = Mac { path, args, prior_type_ascription: self.last_type_ascription };
141 let kind = if delim == token::Brace || self.token == token::Semi || self.token == token::Eof
143 StmtKind::Mac(P((mac, style, attrs.into())))
145 // We used to incorrectly stop parsing macro-expanded statements here.
146 // If the next token will be an error anyway but could have parsed with the
147 // earlier behavior, stop parsing here and emit a warning to avoid breakage.
148 else if legacy_warnings
149 && self.token.can_begin_expr()
150 && match self.token.kind {
151 // These can continue an expression, so we can't stop parsing and warn.
152 token::OpenDelim(token::Paren)
153 | token::OpenDelim(token::Bracket)
154 | token::BinOp(token::Minus)
155 | token::BinOp(token::Star)
156 | token::BinOp(token::And)
157 | token::BinOp(token::Or)
162 | token::DotDotEq => false,
166 self.warn_missing_semicolon();
167 StmtKind::Mac(P((mac, style, attrs)))
169 // Since none of the above applied, this is an expression statement macro.
170 let e = self.mk_expr(lo.to(hi), ExprKind::Mac(mac), AttrVec::new());
171 let e = self.maybe_recover_from_bad_qpath(e, true)?;
172 let e = self.parse_dot_or_call_expr_with(e, lo, attrs)?;
173 let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
176 Ok(Some(self.mk_stmt(lo.to(hi), kind)))
179 /// Error on outer attributes in this context.
180 /// Also error if the previous token was a doc comment.
181 fn error_outer_attrs(&self, attrs: &[Attribute]) {
182 if !attrs.is_empty() {
183 if matches!(self.prev_token.kind, TokenKind::DocComment(..)) {
184 self.span_fatal_err(self.prev_span, Error::UselessDocComment).emit();
185 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
186 self.struct_span_err(self.token.span, "expected statement after outer attribute")
192 fn recover_stmt_local(
198 ) -> PResult<'a, Option<Stmt>> {
199 let stmt = self.parse_local_mk(lo, attrs)?;
200 self.struct_span_err(lo, "invalid variable declaration")
201 .span_suggestion(lo, msg, sugg.to_string(), Applicability::MachineApplicable)
206 fn parse_local_mk(&mut self, lo: Span, attrs: AttrVec) -> PResult<'a, Stmt> {
207 let local = self.parse_local(attrs.into())?;
208 Ok(self.mk_stmt(lo.to(self.prev_span), StmtKind::Local(local)))
211 /// Parses a local variable declaration.
212 fn parse_local(&mut self, attrs: AttrVec) -> PResult<'a, P<Local>> {
213 let lo = self.prev_span;
214 let pat = self.parse_top_pat(GateOr::Yes)?;
216 let (err, ty) = if self.eat(&token::Colon) {
217 // Save the state of the parser before parsing type normally, in case there is a `:`
218 // instead of an `=` typo.
219 let parser_snapshot_before_type = self.clone();
220 let colon_sp = self.prev_span;
221 match self.parse_ty() {
222 Ok(ty) => (None, Some(ty)),
224 // Rewind to before attempting to parse the type and continue parsing.
225 let parser_snapshot_after_type = self.clone();
226 mem::replace(self, parser_snapshot_before_type);
228 let snippet = self.span_to_snippet(pat.span).unwrap();
229 err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
230 (Some((parser_snapshot_after_type, colon_sp, err)), None)
236 let init = match (self.parse_initializer(err.is_some()), err) {
237 (Ok(init), None) => {
238 // init parsed, ty parsed
241 (Ok(init), Some((_, colon_sp, mut err))) => {
242 // init parsed, ty error
243 // Could parse the type as if it were the initializer, it is likely there was a
244 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
245 err.span_suggestion_short(
247 "use `=` if you meant to assign",
249 Applicability::MachineApplicable,
252 // As this was parsed successfully, continue as if the code has been fixed for the
253 // rest of the file. It will still fail due to the emitted error, but we avoid
257 (Err(mut init_err), Some((snapshot, _, ty_err))) => {
258 // init error, ty error
260 // Couldn't parse the type nor the initializer, only raise the type error and
261 // return to the parser state before parsing the type as the initializer.
262 // let x: <parse_error>;
263 mem::replace(self, snapshot);
266 (Err(err), None) => {
267 // init error, ty parsed
268 // Couldn't parse the initializer and we're not attempting to recover a failed
269 // parse of the type, return the error.
273 let hi = if self.token == token::Semi { self.token.span } else { self.prev_span };
274 Ok(P(ast::Local { ty, pat, init, id: DUMMY_NODE_ID, span: lo.to(hi), attrs }))
277 /// Parses the RHS of a local variable declaration (e.g., '= 14;').
278 fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
279 if self.eat(&token::Eq) {
280 Ok(Some(self.parse_expr()?))
282 Ok(Some(self.parse_expr()?))
288 /// Parses a block. No inner attributes are allowed.
289 pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
290 maybe_whole!(self, NtBlock, |x| x);
292 let lo = self.token.span;
294 if !self.eat(&token::OpenDelim(token::Brace)) {
295 return self.error_block_no_opening_brace();
298 self.parse_block_tail(lo, BlockCheckMode::Default)
301 fn error_block_no_opening_brace<T>(&mut self) -> PResult<'a, T> {
302 let sp = self.token.span;
303 let tok = super::token_descr(&self.token);
304 let mut e = self.struct_span_err(sp, &format!("expected `{{`, found {}", tok));
305 let do_not_suggest_help = self.token.is_keyword(kw::In) || self.token == token::Colon;
307 // Check to see if the user has written something like
312 // which is valid in other languages, but not Rust.
313 match self.parse_stmt_without_recovery(false) {
315 if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
316 || do_not_suggest_help
318 // If the next token is an open brace (e.g., `if a b {`), the place-
319 // inside-a-block suggestion would be more likely wrong than right.
320 e.span_label(sp, "expected `{`");
323 let stmt_span = if self.eat(&token::Semi) {
324 // Expand the span to include the semicolon.
325 stmt.span.with_hi(self.prev_span.hi())
329 if let Ok(snippet) = self.span_to_snippet(stmt_span) {
332 "try placing this code inside a block",
333 format!("{{ {} }}", snippet),
334 // Speculative; has been misleading in the past (#46836).
335 Applicability::MaybeIncorrect,
340 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
345 e.span_label(sp, "expected `{`");
349 /// Parses a block. Inner attributes are allowed.
350 pub(super) fn parse_inner_attrs_and_block(
352 ) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
353 maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
355 let lo = self.token.span;
356 self.expect(&token::OpenDelim(token::Brace))?;
357 Ok((self.parse_inner_attributes()?, self.parse_block_tail(lo, BlockCheckMode::Default)?))
360 /// Parses the rest of a block expression or function body.
361 /// Precondition: already parsed the '{'.
362 pub(super) fn parse_block_tail(
366 ) -> PResult<'a, P<Block>> {
367 let mut stmts = vec![];
368 while !self.eat(&token::CloseDelim(token::Brace)) {
369 if self.token == token::Eof {
372 let stmt = match self.parse_full_stmt(false) {
374 self.maybe_annotate_with_ascription(&mut err, false);
376 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
377 Some(self.mk_stmt_err(self.token.span))
381 if let Some(stmt) = stmt {
384 // Found only `;` or `}`.
388 Ok(self.mk_block(stmts, s, lo.to(self.prev_span)))
391 /// Parses a statement, including the trailing semicolon.
392 pub fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
393 // Skip looking for a trailing semicolon when we have an interpolated statement.
394 maybe_whole!(self, NtStmt, |x| Some(x));
396 let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
398 None => return Ok(None),
401 let mut eat_semi = true;
403 StmtKind::Expr(ref expr) if self.token != token::Eof => {
404 // expression without semicolon
405 if classify::expr_requires_semi_to_be_stmt(expr) {
406 // Just check for errors and recover; do not eat semicolon yet.
408 self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
410 if let TokenKind::DocComment(..) = self.token.kind {
411 if let Ok(snippet) = self.span_to_snippet(self.token.span) {
412 let sp = self.token.span;
413 let marker = &snippet[..3];
414 let (comment_marker, doc_comment_marker) = marker.split_at(2);
417 sp.with_hi(sp.lo() + BytePos(marker.len() as u32)),
419 "add a space before `{}` to use a regular comment",
422 format!("{} {}", comment_marker, doc_comment_marker),
423 Applicability::MaybeIncorrect,
429 // Don't complain about type errors in body tail after parse error (#57383).
430 let sp = expr.span.to(self.prev_span);
431 stmt.kind = StmtKind::Expr(self.mk_expr_err(sp));
435 StmtKind::Local(..) => {
436 // We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
437 if macro_legacy_warnings && self.token != token::Semi {
438 self.warn_missing_semicolon();
447 if eat_semi && self.eat(&token::Semi) {
448 stmt = stmt.add_trailing_semicolon();
450 stmt.span = stmt.span.to(self.prev_span);
454 fn warn_missing_semicolon(&self) {
456 .struct_span_warn(self.token.span, {
457 &format!("expected `;`, found {}", super::token_descr(&self.token))
460 "this was erroneously allowed and will become a hard error in a future release"
465 pub(super) fn mk_block(&self, stmts: Vec<Stmt>, rules: BlockCheckMode, span: Span) -> P<Block> {
466 P(Block { stmts, id: DUMMY_NODE_ID, rules, span })
469 pub(super) fn mk_stmt(&self, span: Span, kind: StmtKind) -> Stmt {
470 Stmt { id: DUMMY_NODE_ID, kind, span }
473 fn mk_stmt_err(&self, span: Span) -> Stmt {
474 self.mk_stmt(span, StmtKind::Expr(self.mk_expr_err(span)))
477 pub(super) fn mk_block_err(&self, span: Span) -> P<Block> {
478 self.mk_block(vec![self.mk_stmt_err(span)], BlockCheckMode::Default, span)