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;
10 use rustc_ast::ast::{AttrStyle, AttrVec, Attribute, Mac, MacStmtStyle};
11 use rustc_ast::ast::{Block, BlockCheckMode, Expr, ExprKind, Local, Stmt, StmtKind, DUMMY_NODE_ID};
12 use rustc_ast::ptr::P;
13 use rustc_ast::token::{self, TokenKind};
14 use rustc_ast::util::classify;
15 use rustc_errors::{Applicability, PResult};
16 use rustc_span::source_map::{BytePos, Span};
17 use rustc_span::symbol::{kw, sym};
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 let stmt = if self.eat_keyword(kw::Let) {
39 self.parse_local_mk(lo, attrs.into())?
40 } else if self.is_kw_followed_by_ident(kw::Mut) {
41 self.recover_stmt_local(lo, attrs.into(), "missing keyword", "let mut")?
42 } else if self.is_kw_followed_by_ident(kw::Auto) {
43 self.bump(); // `auto`
44 let msg = "write `let` instead of `auto` to introduce a new variable";
45 self.recover_stmt_local(lo, attrs.into(), msg, "let")?
46 } else if self.is_kw_followed_by_ident(sym::var) {
48 let msg = "write `let` instead of `var` to introduce a new variable";
49 self.recover_stmt_local(lo, attrs.into(), msg, "let")?
50 } else if self.token.is_path_start()
51 && !self.token.is_qpath_start()
52 && !self.is_path_start_item()
54 // We have avoided contextual keywords like `union`, items with `crate` visibility,
55 // or `auto trait` items. We aim to parse an arbitrary path `a::b` but not something
56 // that starts like a path (1 token), but it fact not a path.
57 // Also, we avoid stealing syntax from `parse_item_`.
58 self.parse_stmt_path_start(lo, attrs)?
59 } else if let Some(item) = self.parse_stmt_item(attrs.clone())? {
60 // FIXME: Bad copy of attrs
61 self.mk_stmt(lo.to(item.span), StmtKind::Item(P(item)))
62 } else if self.token == token::Semi {
63 // Do not attempt to parse an expression if we're done here.
64 self.error_outer_attrs(&attrs);
66 let mut last_semi = lo;
67 while self.token == token::Semi {
68 last_semi = self.token.span;
71 // We are encoding a string of semicolons as an an empty tuple that spans
72 // the excess semicolons to preserve this info until the lint stage.
73 let kind = StmtKind::Semi(self.mk_expr(
75 ExprKind::Tup(Vec::new()),
78 self.mk_stmt(lo.to(last_semi), kind)
79 } else if self.token != token::CloseDelim(token::Brace) {
80 // Remainder are line-expr stmts.
81 let e = self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs.into()))?;
82 self.mk_stmt(lo.to(e.span), StmtKind::Expr(e))
84 self.error_outer_attrs(&attrs);
90 fn parse_stmt_item(&mut self, attrs: Vec<Attribute>) -> PResult<'a, Option<ast::Item>> {
91 let old = mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
92 let item = self.parse_item_common(attrs, false, true, |_| true)?;
93 self.directory.ownership = old;
97 fn parse_stmt_path_start(&mut self, lo: Span, attrs: Vec<Attribute>) -> PResult<'a, Stmt> {
98 let path = self.parse_path(PathStyle::Expr)?;
100 if self.eat(&token::Not) {
101 return self.parse_stmt_mac(lo, attrs.into(), path);
104 let expr = if self.check(&token::OpenDelim(token::Brace)) {
105 self.parse_struct_expr(lo, path, AttrVec::new())?
107 let hi = self.prev_token.span;
108 self.mk_expr(lo.to(hi), ExprKind::Path(None, path), AttrVec::new())
111 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
112 let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
113 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
115 Ok(self.mk_stmt(lo.to(self.prev_token.span), StmtKind::Expr(expr)))
118 /// Parses a statement macro `mac!(args)` provided a `path` representing `mac`.
119 /// At this point, the `!` token after the path has already been eaten.
120 fn parse_stmt_mac(&mut self, lo: Span, attrs: AttrVec, path: ast::Path) -> PResult<'a, Stmt> {
121 let args = self.parse_mac_args()?;
122 let delim = args.delim();
123 let hi = self.prev_token.span;
126 if delim == token::Brace { MacStmtStyle::Braces } else { MacStmtStyle::NoBraces };
128 let mac = Mac { path, args, prior_type_ascription: self.last_type_ascription };
130 let kind = if delim == token::Brace || self.token == token::Semi || self.token == token::Eof
132 StmtKind::Mac(P((mac, style, attrs)))
134 // Since none of the above applied, this is an expression statement macro.
135 let e = self.mk_expr(lo.to(hi), ExprKind::Mac(mac), AttrVec::new());
136 let e = self.maybe_recover_from_bad_qpath(e, true)?;
137 let e = self.parse_dot_or_call_expr_with(e, lo, attrs)?;
138 let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
141 Ok(self.mk_stmt(lo.to(hi), kind))
144 /// Error on outer attributes in this context.
145 /// Also error if the previous token was a doc comment.
146 fn error_outer_attrs(&self, attrs: &[Attribute]) {
147 if !attrs.is_empty() {
148 if matches!(self.prev_token.kind, TokenKind::DocComment(..)) {
149 self.span_fatal_err(self.prev_token.span, Error::UselessDocComment).emit();
150 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
151 self.struct_span_err(self.token.span, "expected statement after outer attribute")
157 fn recover_stmt_local(
163 ) -> PResult<'a, Stmt> {
164 let stmt = self.parse_local_mk(lo, attrs)?;
165 self.struct_span_err(lo, "invalid variable declaration")
166 .span_suggestion(lo, msg, sugg.to_string(), Applicability::MachineApplicable)
171 fn parse_local_mk(&mut self, lo: Span, attrs: AttrVec) -> PResult<'a, Stmt> {
172 let local = self.parse_local(attrs)?;
173 Ok(self.mk_stmt(lo.to(self.prev_token.span), StmtKind::Local(local)))
176 /// Parses a local variable declaration.
177 fn parse_local(&mut self, attrs: AttrVec) -> PResult<'a, P<Local>> {
178 let lo = self.prev_token.span;
179 let pat = self.parse_top_pat(GateOr::Yes)?;
181 let (err, ty) = if self.eat(&token::Colon) {
182 // Save the state of the parser before parsing type normally, in case there is a `:`
183 // instead of an `=` typo.
184 let parser_snapshot_before_type = self.clone();
185 let colon_sp = self.prev_token.span;
186 match self.parse_ty() {
187 Ok(ty) => (None, Some(ty)),
189 // Rewind to before attempting to parse the type and continue parsing.
190 let parser_snapshot_after_type = self.clone();
191 mem::replace(self, parser_snapshot_before_type);
193 let snippet = self.span_to_snippet(pat.span).unwrap();
194 err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
195 (Some((parser_snapshot_after_type, colon_sp, err)), None)
201 let init = match (self.parse_initializer(err.is_some()), err) {
202 (Ok(init), None) => {
203 // init parsed, ty parsed
206 (Ok(init), Some((_, colon_sp, mut err))) => {
207 // init parsed, ty error
208 // Could parse the type as if it were the initializer, it is likely there was a
209 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
210 err.span_suggestion_short(
212 "use `=` if you meant to assign",
214 Applicability::MachineApplicable,
217 // As this was parsed successfully, continue as if the code has been fixed for the
218 // rest of the file. It will still fail due to the emitted error, but we avoid
222 (Err(mut init_err), Some((snapshot, _, ty_err))) => {
223 // init error, ty error
225 // Couldn't parse the type nor the initializer, only raise the type error and
226 // return to the parser state before parsing the type as the initializer.
227 // let x: <parse_error>;
228 mem::replace(self, snapshot);
231 (Err(err), None) => {
232 // init error, ty parsed
233 // Couldn't parse the initializer and we're not attempting to recover a failed
234 // parse of the type, return the error.
238 let hi = if self.token == token::Semi { self.token.span } else { self.prev_token.span };
239 Ok(P(ast::Local { ty, pat, init, id: DUMMY_NODE_ID, span: lo.to(hi), attrs }))
242 /// Parses the RHS of a local variable declaration (e.g., '= 14;').
243 fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
244 if self.eat(&token::Eq) {
245 Ok(Some(self.parse_expr()?))
247 Ok(Some(self.parse_expr()?))
253 /// Parses a block. No inner attributes are allowed.
254 pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
255 maybe_whole!(self, NtBlock, |x| x);
257 let lo = self.token.span;
259 if !self.eat(&token::OpenDelim(token::Brace)) {
260 return self.error_block_no_opening_brace();
263 self.parse_block_tail(lo, BlockCheckMode::Default)
266 fn error_block_no_opening_brace<T>(&mut self) -> PResult<'a, T> {
267 let sp = self.token.span;
268 let tok = super::token_descr(&self.token);
269 let mut e = self.struct_span_err(sp, &format!("expected `{{`, found {}", tok));
270 let do_not_suggest_help = self.token.is_keyword(kw::In) || self.token == token::Colon;
272 // Check to see if the user has written something like
277 // which is valid in other languages, but not Rust.
278 match self.parse_stmt_without_recovery() {
280 if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
281 || do_not_suggest_help
283 // If the next token is an open brace (e.g., `if a b {`), the place-
284 // inside-a-block suggestion would be more likely wrong than right.
285 e.span_label(sp, "expected `{`");
288 let stmt_span = if self.eat(&token::Semi) {
289 // Expand the span to include the semicolon.
290 stmt.span.with_hi(self.prev_token.span.hi())
294 if let Ok(snippet) = self.span_to_snippet(stmt_span) {
297 "try placing this code inside a block",
298 format!("{{ {} }}", snippet),
299 // Speculative; has been misleading in the past (#46836).
300 Applicability::MaybeIncorrect,
305 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
310 e.span_label(sp, "expected `{`");
314 /// Parses a block. Inner attributes are allowed.
315 pub(super) fn parse_inner_attrs_and_block(
317 ) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
318 maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
320 let lo = self.token.span;
321 self.expect(&token::OpenDelim(token::Brace))?;
322 Ok((self.parse_inner_attributes()?, self.parse_block_tail(lo, BlockCheckMode::Default)?))
325 /// Parses the rest of a block expression or function body.
326 /// Precondition: already parsed the '{'.
327 pub(super) fn parse_block_tail(
331 ) -> PResult<'a, P<Block>> {
332 let mut stmts = vec![];
333 while !self.eat(&token::CloseDelim(token::Brace)) {
334 if self.token == token::Eof {
337 let stmt = match self.parse_full_stmt() {
339 self.maybe_annotate_with_ascription(&mut err, false);
341 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
342 Some(self.mk_stmt_err(self.token.span))
346 if let Some(stmt) = stmt {
349 // Found only `;` or `}`.
353 Ok(self.mk_block(stmts, s, lo.to(self.prev_token.span)))
356 /// Parses a statement, including the trailing semicolon.
357 pub fn parse_full_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
358 // Skip looking for a trailing semicolon when we have an interpolated statement.
359 maybe_whole!(self, NtStmt, |x| Some(x));
361 let mut stmt = match self.parse_stmt_without_recovery()? {
363 None => return Ok(None),
366 let mut eat_semi = true;
368 // Expression without semicolon.
369 StmtKind::Expr(ref expr)
370 if self.token != token::Eof && classify::expr_requires_semi_to_be_stmt(expr) =>
372 // Just check for errors and recover; do not eat semicolon yet.
374 self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
376 if let TokenKind::DocComment(..) = self.token.kind {
377 if let Ok(snippet) = self.span_to_snippet(self.token.span) {
378 let sp = self.token.span;
379 let marker = &snippet[..3];
380 let (comment_marker, doc_comment_marker) = marker.split_at(2);
383 sp.with_hi(sp.lo() + BytePos(marker.len() as u32)),
385 "add a space before `{}` to use a regular comment",
388 format!("{} {}", comment_marker, doc_comment_marker),
389 Applicability::MaybeIncorrect,
395 // Don't complain about type errors in body tail after parse error (#57383).
396 let sp = expr.span.to(self.prev_token.span);
397 stmt.kind = StmtKind::Expr(self.mk_expr_err(sp));
400 StmtKind::Local(..) => {
407 if eat_semi && self.eat(&token::Semi) {
408 stmt = stmt.add_trailing_semicolon();
410 stmt.span = stmt.span.to(self.prev_token.span);
414 pub(super) fn mk_block(&self, stmts: Vec<Stmt>, rules: BlockCheckMode, span: Span) -> P<Block> {
415 P(Block { stmts, id: DUMMY_NODE_ID, rules, span })
418 pub(super) fn mk_stmt(&self, span: Span, kind: StmtKind) -> Stmt {
419 Stmt { id: DUMMY_NODE_ID, kind, span }
422 fn mk_stmt_err(&self, span: Span) -> Stmt {
423 self.mk_stmt(span, StmtKind::Expr(self.mk_expr_err(span)))
426 pub(super) fn mk_block_err(&self, span: Span) -> P<Block> {
427 self.mk_block(vec![self.mk_stmt_err(span)], BlockCheckMode::Default, span)