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.eat(&token::Semi) {
63 // Do not attempt to parse an expression if we're done here.
64 self.error_outer_attrs(&attrs);
65 self.mk_stmt(lo, StmtKind::Empty)
66 } else if self.token != token::CloseDelim(token::Brace) {
67 // Remainder are line-expr stmts.
68 let e = self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs.into()))?;
69 self.mk_stmt(lo.to(e.span), StmtKind::Expr(e))
71 self.error_outer_attrs(&attrs);
77 fn parse_stmt_item(&mut self, attrs: Vec<Attribute>) -> PResult<'a, Option<ast::Item>> {
78 let old = mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
79 let item = self.parse_item_common(attrs, false, true, |_| true)?;
80 self.directory.ownership = old;
84 fn parse_stmt_path_start(&mut self, lo: Span, attrs: Vec<Attribute>) -> PResult<'a, Stmt> {
85 let path = self.parse_path(PathStyle::Expr)?;
87 if self.eat(&token::Not) {
88 return self.parse_stmt_mac(lo, attrs.into(), path);
91 let expr = if self.check(&token::OpenDelim(token::Brace)) {
92 self.parse_struct_expr(lo, path, AttrVec::new())?
94 let hi = self.prev_token.span;
95 self.mk_expr(lo.to(hi), ExprKind::Path(None, path), AttrVec::new())
98 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
99 let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
100 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
102 Ok(self.mk_stmt(lo.to(self.prev_token.span), StmtKind::Expr(expr)))
105 /// Parses a statement macro `mac!(args)` provided a `path` representing `mac`.
106 /// At this point, the `!` token after the path has already been eaten.
107 fn parse_stmt_mac(&mut self, lo: Span, attrs: AttrVec, path: ast::Path) -> PResult<'a, Stmt> {
108 let args = self.parse_mac_args()?;
109 let delim = args.delim();
110 let hi = self.prev_token.span;
113 if delim == token::Brace { MacStmtStyle::Braces } else { MacStmtStyle::NoBraces };
115 let mac = Mac { path, args, prior_type_ascription: self.last_type_ascription };
117 let kind = if delim == token::Brace || self.token == token::Semi || self.token == token::Eof
119 StmtKind::Mac(P((mac, style, attrs)))
121 // Since none of the above applied, this is an expression statement macro.
122 let e = self.mk_expr(lo.to(hi), ExprKind::Mac(mac), AttrVec::new());
123 let e = self.maybe_recover_from_bad_qpath(e, true)?;
124 let e = self.parse_dot_or_call_expr_with(e, lo, attrs)?;
125 let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
128 Ok(self.mk_stmt(lo.to(hi), kind))
131 /// Error on outer attributes in this context.
132 /// Also error if the previous token was a doc comment.
133 fn error_outer_attrs(&self, attrs: &[Attribute]) {
134 if let [.., last] = attrs {
135 if last.is_doc_comment() {
136 self.span_fatal_err(last.span, Error::UselessDocComment).emit();
137 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
138 self.struct_span_err(last.span, "expected statement after outer attribute").emit();
143 fn recover_stmt_local(
149 ) -> PResult<'a, Stmt> {
150 let stmt = self.parse_local_mk(lo, attrs)?;
151 self.struct_span_err(lo, "invalid variable declaration")
152 .span_suggestion(lo, msg, sugg.to_string(), Applicability::MachineApplicable)
157 fn parse_local_mk(&mut self, lo: Span, attrs: AttrVec) -> PResult<'a, Stmt> {
158 let local = self.parse_local(attrs)?;
159 Ok(self.mk_stmt(lo.to(self.prev_token.span), StmtKind::Local(local)))
162 /// Parses a local variable declaration.
163 fn parse_local(&mut self, attrs: AttrVec) -> PResult<'a, P<Local>> {
164 let lo = self.prev_token.span;
165 let pat = self.parse_top_pat(GateOr::Yes)?;
167 let (err, ty) = if self.eat(&token::Colon) {
168 // Save the state of the parser before parsing type normally, in case there is a `:`
169 // instead of an `=` typo.
170 let parser_snapshot_before_type = self.clone();
171 let colon_sp = self.prev_token.span;
172 match self.parse_ty() {
173 Ok(ty) => (None, Some(ty)),
175 // Rewind to before attempting to parse the type and continue parsing.
176 let parser_snapshot_after_type = self.clone();
177 mem::replace(self, parser_snapshot_before_type);
179 let snippet = self.span_to_snippet(pat.span).unwrap();
180 err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
181 (Some((parser_snapshot_after_type, colon_sp, err)), None)
187 let init = match (self.parse_initializer(err.is_some()), err) {
188 (Ok(init), None) => {
189 // init parsed, ty parsed
192 (Ok(init), Some((_, colon_sp, mut err))) => {
193 // init parsed, ty error
194 // Could parse the type as if it were the initializer, it is likely there was a
195 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
196 err.span_suggestion_short(
198 "use `=` if you meant to assign",
200 Applicability::MachineApplicable,
203 // As this was parsed successfully, continue as if the code has been fixed for the
204 // rest of the file. It will still fail due to the emitted error, but we avoid
208 (Err(mut init_err), Some((snapshot, _, ty_err))) => {
209 // init error, ty error
211 // Couldn't parse the type nor the initializer, only raise the type error and
212 // return to the parser state before parsing the type as the initializer.
213 // let x: <parse_error>;
214 mem::replace(self, snapshot);
217 (Err(err), None) => {
218 // init error, ty parsed
219 // Couldn't parse the initializer and we're not attempting to recover a failed
220 // parse of the type, return the error.
224 let hi = if self.token == token::Semi { self.token.span } else { self.prev_token.span };
225 Ok(P(ast::Local { ty, pat, init, id: DUMMY_NODE_ID, span: lo.to(hi), attrs }))
228 /// Parses the RHS of a local variable declaration (e.g., '= 14;').
229 fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
230 if self.eat(&token::Eq) {
231 Ok(Some(self.parse_expr()?))
233 Ok(Some(self.parse_expr()?))
239 /// Parses a block. No inner attributes are allowed.
240 pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
241 maybe_whole!(self, NtBlock, |x| x);
243 let lo = self.token.span;
245 if !self.eat(&token::OpenDelim(token::Brace)) {
246 return self.error_block_no_opening_brace();
249 self.parse_block_tail(lo, BlockCheckMode::Default)
252 fn error_block_no_opening_brace<T>(&mut self) -> PResult<'a, T> {
253 let sp = self.token.span;
254 let tok = super::token_descr(&self.token);
255 let mut e = self.struct_span_err(sp, &format!("expected `{{`, found {}", tok));
256 let do_not_suggest_help = self.token.is_keyword(kw::In) || self.token == token::Colon;
258 // Check to see if the user has written something like
263 // which is valid in other languages, but not Rust.
264 match self.parse_stmt_without_recovery() {
266 if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
267 || do_not_suggest_help
269 // If the next token is an open brace (e.g., `if a b {`), the place-
270 // inside-a-block suggestion would be more likely wrong than right.
271 e.span_label(sp, "expected `{`");
274 let stmt_span = if self.eat(&token::Semi) {
275 // Expand the span to include the semicolon.
276 stmt.span.with_hi(self.prev_token.span.hi())
280 if let Ok(snippet) = self.span_to_snippet(stmt_span) {
283 "try placing this code inside a block",
284 format!("{{ {} }}", snippet),
285 // Speculative; has been misleading in the past (#46836).
286 Applicability::MaybeIncorrect,
291 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
296 e.span_label(sp, "expected `{`");
300 /// Parses a block. Inner attributes are allowed.
301 pub(super) fn parse_inner_attrs_and_block(
303 ) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
304 maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
306 let lo = self.token.span;
307 self.expect(&token::OpenDelim(token::Brace))?;
308 Ok((self.parse_inner_attributes()?, self.parse_block_tail(lo, BlockCheckMode::Default)?))
311 /// Parses the rest of a block expression or function body.
312 /// Precondition: already parsed the '{'.
313 pub(super) fn parse_block_tail(
317 ) -> PResult<'a, P<Block>> {
318 let mut stmts = vec![];
319 while !self.eat(&token::CloseDelim(token::Brace)) {
320 if self.token == token::Eof {
323 let stmt = match self.parse_full_stmt() {
325 self.maybe_annotate_with_ascription(&mut err, false);
327 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
328 Some(self.mk_stmt_err(self.token.span))
332 if let Some(stmt) = stmt {
335 // Found only `;` or `}`.
339 Ok(self.mk_block(stmts, s, lo.to(self.prev_token.span)))
342 /// Parses a statement, including the trailing semicolon.
343 pub fn parse_full_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
344 // Skip looking for a trailing semicolon when we have an interpolated statement.
345 maybe_whole!(self, NtStmt, |x| Some(x));
347 let mut stmt = match self.parse_stmt_without_recovery()? {
349 None => return Ok(None),
352 let mut eat_semi = true;
354 // Expression without semicolon.
355 StmtKind::Expr(ref expr)
356 if self.token != token::Eof && classify::expr_requires_semi_to_be_stmt(expr) =>
358 // Just check for errors and recover; do not eat semicolon yet.
360 self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
362 if let TokenKind::DocComment(..) = self.token.kind {
363 if let Ok(snippet) = self.span_to_snippet(self.token.span) {
364 let sp = self.token.span;
365 let marker = &snippet[..3];
366 let (comment_marker, doc_comment_marker) = marker.split_at(2);
369 sp.with_hi(sp.lo() + BytePos(marker.len() as u32)),
371 "add a space before `{}` to use a regular comment",
374 format!("{} {}", comment_marker, doc_comment_marker),
375 Applicability::MaybeIncorrect,
381 // Don't complain about type errors in body tail after parse error (#57383).
382 let sp = expr.span.to(self.prev_token.span);
383 stmt.kind = StmtKind::Expr(self.mk_expr_err(sp));
386 StmtKind::Local(..) => {
390 StmtKind::Empty => eat_semi = false,
394 if eat_semi && self.eat(&token::Semi) {
395 stmt = stmt.add_trailing_semicolon();
397 stmt.span = stmt.span.to(self.prev_token.span);
401 pub(super) fn mk_block(&self, stmts: Vec<Stmt>, rules: BlockCheckMode, span: Span) -> P<Block> {
402 P(Block { stmts, id: DUMMY_NODE_ID, rules, span })
405 pub(super) fn mk_stmt(&self, span: Span, kind: StmtKind) -> Stmt {
406 Stmt { id: DUMMY_NODE_ID, kind, span }
409 fn mk_stmt_err(&self, span: Span) -> Stmt {
410 self.mk_stmt(span, StmtKind::Expr(self.mk_expr_err(span)))
413 pub(super) fn mk_block_err(&self, span: Span) -> P<Block> {
414 self.mk_block(vec![self.mk_stmt_err(span)], BlockCheckMode::Default, span)