compiler/rustc_parse/src/parser/stmt.rs

   1 use super::attr::InnerAttrForbiddenReason;
   2 use super::diagnostics::AttemptLocalParseRecovery;
   3 use super::expr::LhsExpr;
   4 use super::pat::{PatternLocation, RecoverComma};
   5 use super::path::PathStyle;
   6 use super::TrailingToken;
   7 use super::{
   8     AttrWrapper, BlockMode, FnParseMode, ForceCollect, Parser, Restrictions, SemiColonMode,
   9 };
  10 use crate::errors::{
  11     AssignmentElseNotAllowed, CompoundAssignmentExpressionInLet, ConstLetMutuallyExclusive,
  12     DocCommentDoesNotDocumentAnything, ExpectedStatementAfterOuterAttr, InvalidCurlyInLetElse,
  13     InvalidExpressionInLetElse, InvalidIdentiferStartsWithNumber, InvalidVariableDeclaration,
  14     InvalidVariableDeclarationSub, WrapExpressionInParentheses,
  15 };
  16 use crate::maybe_whole;
  17
  18 use rustc_ast as ast;
  19 use rustc_ast::ptr::P;
  20 use rustc_ast::token::{self, Delimiter, TokenKind};
  21 use rustc_ast::util::classify;
  22 use rustc_ast::{AttrStyle, AttrVec, LocalKind, MacCall, MacCallStmt, MacStmtStyle};
  23 use rustc_ast::{Block, BlockCheckMode, Expr, ExprKind, HasAttrs, Local, Stmt};
  24 use rustc_ast::{StmtKind, DUMMY_NODE_ID};
  25 use rustc_errors::{Applicability, DiagnosticBuilder, ErrorGuaranteed, PResult};
  26 use rustc_span::source_map::{BytePos, Span};
  27 use rustc_span::symbol::{kw, sym};
  28
  29 use std::mem;
  30
  31 impl<'a> Parser<'a> {
  32     /// Parses a statement. This stops just before trailing semicolons on everything but items.
  33     /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
  34     // Public for rustfmt usage.
  35     pub fn parse_stmt(&mut self, force_collect: ForceCollect) -> PResult<'a, Option<Stmt>> {
  36         Ok(self.parse_stmt_without_recovery(false, force_collect).unwrap_or_else(|mut e| {
  37             e.emit();
  38             self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
  39             None
  40         }))
  41     }
  42
  43     /// If `force_collect` is [`ForceCollect::Yes`], forces collection of tokens regardless of whether
  44     /// or not we have attributes
  45     pub(crate) fn parse_stmt_without_recovery(
  46         &mut self,
  47         capture_semi: bool,
  48         force_collect: ForceCollect,
  49     ) -> PResult<'a, Option<Stmt>> {
  50         let attrs = self.parse_outer_attributes()?;
  51         let lo = self.token.span;
  52
  53         // Don't use `maybe_whole` so that we have precise control
  54         // over when we bump the parser
  55         if let token::Interpolated(nt) = &self.token.kind && let token::NtStmt(stmt) = &**nt {
  56             let mut stmt = stmt.clone();
  57             self.bump();
  58             stmt.visit_attrs(|stmt_attrs| {
  59                 attrs.prepend_to_nt_inner(stmt_attrs);
  60             });
  61             return Ok(Some(stmt.into_inner()));
  62         }
  63
  64         if self.token.is_keyword(kw::Mut) && self.is_keyword_ahead(1, &[kw::Let]) {
  65             self.bump();
  66             let mut_let_span = lo.to(self.token.span);
  67             self.sess.emit_err(InvalidVariableDeclaration {
  68                 span: mut_let_span,
  69                 sub: InvalidVariableDeclarationSub::SwitchMutLetOrder(mut_let_span),
  70             });
  71         }
  72
  73         Ok(Some(if self.token.is_keyword(kw::Let) {
  74             self.parse_local_mk(lo, attrs, capture_semi, force_collect)?
  75         } else if self.is_kw_followed_by_ident(kw::Mut) && self.may_recover() {
  76             self.recover_stmt_local_after_let(lo, attrs, InvalidVariableDeclarationSub::MissingLet)?
  77         } else if self.is_kw_followed_by_ident(kw::Auto) && self.may_recover() {
  78             self.bump(); // `auto`
  79             self.recover_stmt_local_after_let(
  80                 lo,
  81                 attrs,
  82                 InvalidVariableDeclarationSub::UseLetNotAuto,
  83             )?
  84         } else if self.is_kw_followed_by_ident(sym::var) && self.may_recover() {
  85             self.bump(); // `var`
  86             self.recover_stmt_local_after_let(
  87                 lo,
  88                 attrs,
  89                 InvalidVariableDeclarationSub::UseLetNotVar,
  90             )?
  91         } else if self.check_path() && !self.token.is_qpath_start() && !self.is_path_start_item() {
  92             // We have avoided contextual keywords like `union`, items with `crate` visibility,
  93             // or `auto trait` items. We aim to parse an arbitrary path `a::b` but not something
  94             // that starts like a path (1 token), but it fact not a path.
  95             // Also, we avoid stealing syntax from `parse_item_`.
  96             match force_collect {
  97                 ForceCollect::Yes => {
  98                     self.collect_tokens_no_attrs(|this| this.parse_stmt_path_start(lo, attrs))?
  99                 }
 100                 ForceCollect::No => self.parse_stmt_path_start(lo, attrs)?,
 101             }
 102         } else if let Some(item) = self.parse_item_common(
 103             attrs.clone(),
 104             false,
 105             true,
 106             FnParseMode { req_name: |_| true, req_body: true },
 107             force_collect,
 108         )? {
 109             // FIXME: Bad copy of attrs
 110             self.mk_stmt(lo.to(item.span), StmtKind::Item(P(item)))
 111         } else if self.eat(&token::Semi) {
 112             // Do not attempt to parse an expression if we're done here.
 113             self.error_outer_attrs(attrs);
 114             self.mk_stmt(lo, StmtKind::Empty)
 115         } else if self.token != token::CloseDelim(Delimiter::Brace) {
 116             // Remainder are line-expr stmts.
 117             let e = match force_collect {
 118                 ForceCollect::Yes => self.collect_tokens_no_attrs(|this| {
 119                     this.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs))
 120                 })?,
 121                 ForceCollect::No => self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs))?,
 122             };
 123             if matches!(e.kind, ExprKind::Assign(..)) && self.eat_keyword(kw::Else) {
 124                 let bl = self.parse_block()?;
 125                 // Destructuring assignment ... else.
 126                 // This is not allowed, but point it out in a nice way.
 127                 self.sess.emit_err(AssignmentElseNotAllowed { span: e.span.to(bl.span) });
 128             }
 129             self.mk_stmt(lo.to(e.span), StmtKind::Expr(e))
 130         } else {
 131             self.error_outer_attrs(attrs);
 132             return Ok(None);
 133         }))
 134     }
 135
 136     fn parse_stmt_path_start(&mut self, lo: Span, attrs: AttrWrapper) -> PResult<'a, Stmt> {
 137         let stmt = self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
 138             let path = this.parse_path(PathStyle::Expr)?;
 139
 140             if this.eat(&token::Not) {
 141                 let stmt_mac = this.parse_stmt_mac(lo, attrs, path)?;
 142                 if this.token == token::Semi {
 143                     return Ok((stmt_mac, TrailingToken::Semi));
 144                 } else {
 145                     return Ok((stmt_mac, TrailingToken::None));
 146                 }
 147             }
 148
 149             let expr = if this.eat(&token::OpenDelim(Delimiter::Brace)) {
 150                 this.parse_struct_expr(None, path, true)?
 151             } else {
 152                 let hi = this.prev_token.span;
 153                 this.mk_expr(lo.to(hi), ExprKind::Path(None, path))
 154             };
 155
 156             let expr = this.with_res(Restrictions::STMT_EXPR, |this| {
 157                 this.parse_dot_or_call_expr_with(expr, lo, attrs)
 158             })?;
 159             // `DUMMY_SP` will get overwritten later in this function
 160             Ok((this.mk_stmt(rustc_span::DUMMY_SP, StmtKind::Expr(expr)), TrailingToken::None))
 161         })?;
 162
 163         if let StmtKind::Expr(expr) = stmt.kind {
 164             // Perform this outside of the `collect_tokens_trailing_token` closure,
 165             // since our outer attributes do not apply to this part of the expression
 166             let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
 167                 this.parse_assoc_expr_with(
 168                     0,
 169                     LhsExpr::AlreadyParsed { expr, starts_statement: true },
 170                 )
 171             })?;
 172             Ok(self.mk_stmt(lo.to(self.prev_token.span), StmtKind::Expr(expr)))
 173         } else {
 174             Ok(stmt)
 175         }
 176     }
 177
 178     /// Parses a statement macro `mac!(args)` provided a `path` representing `mac`.
 179     /// At this point, the `!` token after the path has already been eaten.
 180     fn parse_stmt_mac(&mut self, lo: Span, attrs: AttrVec, path: ast::Path) -> PResult<'a, Stmt> {
 181         let args = self.parse_delim_args()?;
 182         let delim = args.delim.to_token();
 183         let hi = self.prev_token.span;
 184
 185         let style = match delim {
 186             Delimiter::Brace => MacStmtStyle::Braces,
 187             _ => MacStmtStyle::NoBraces,
 188         };
 189
 190         let mac = P(MacCall { path, args, prior_type_ascription: self.last_type_ascription });
 191
 192         let kind = if (style == MacStmtStyle::Braces
 193             && self.token != token::Dot
 194             && self.token != token::Question)
 195             || self.token == token::Semi
 196             || self.token == token::Eof
 197         {
 198             StmtKind::MacCall(P(MacCallStmt { mac, style, attrs, tokens: None }))
 199         } else {
 200             // Since none of the above applied, this is an expression statement macro.
 201             let e = self.mk_expr(lo.to(hi), ExprKind::MacCall(mac));
 202             let e = self.maybe_recover_from_bad_qpath(e)?;
 203             let e = self.parse_dot_or_call_expr_with(e, lo, attrs)?;
 204             let e = self.parse_assoc_expr_with(
 205                 0,
 206                 LhsExpr::AlreadyParsed { expr: e, starts_statement: false },
 207             )?;
 208             StmtKind::Expr(e)
 209         };
 210         Ok(self.mk_stmt(lo.to(hi), kind))
 211     }
 212
 213     /// Error on outer attributes in this context.
 214     /// Also error if the previous token was a doc comment.
 215     fn error_outer_attrs(&self, attrs: AttrWrapper) {
 216         if !attrs.is_empty()
 217         && let attrs = attrs.take_for_recovery(self.sess)
 218         && let attrs @ [.., last] = &*attrs {
 219             if last.is_doc_comment() {
 220                 self.sess.emit_err(DocCommentDoesNotDocumentAnything {
 221                     span: last.span,
 222                     missing_comma: None,
 223                 });
 224             } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
 225                 self.sess.emit_err(ExpectedStatementAfterOuterAttr { span: last.span });
 226             }
 227         }
 228     }
 229
 230     fn recover_stmt_local_after_let(
 231         &mut self,
 232         lo: Span,
 233         attrs: AttrWrapper,
 234         subdiagnostic: fn(Span) -> InvalidVariableDeclarationSub,
 235     ) -> PResult<'a, Stmt> {
 236         let stmt =
 237             self.collect_tokens_trailing_token(attrs, ForceCollect::Yes, |this, attrs| {
 238                 let local = this.parse_local(attrs)?;
 239                 // FIXME - maybe capture semicolon in recovery?
 240                 Ok((
 241                     this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Local(local)),
 242                     TrailingToken::None,
 243                 ))
 244             })?;
 245         self.sess.emit_err(InvalidVariableDeclaration { span: lo, sub: subdiagnostic(lo) });
 246         Ok(stmt)
 247     }
 248
 249     fn parse_local_mk(
 250         &mut self,
 251         lo: Span,
 252         attrs: AttrWrapper,
 253         capture_semi: bool,
 254         force_collect: ForceCollect,
 255     ) -> PResult<'a, Stmt> {
 256         self.collect_tokens_trailing_token(attrs, force_collect, |this, attrs| {
 257             this.expect_keyword(kw::Let)?;
 258             let local = this.parse_local(attrs)?;
 259             let trailing = if capture_semi && this.token.kind == token::Semi {
 260                 TrailingToken::Semi
 261             } else {
 262                 TrailingToken::None
 263             };
 264             Ok((this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Local(local)), trailing))
 265         })
 266     }
 267
 268     /// Parses a local variable declaration.
 269     fn parse_local(&mut self, attrs: AttrVec) -> PResult<'a, P<Local>> {
 270         let lo = self.prev_token.span;
 271
 272         if self.token.is_keyword(kw::Const) && self.look_ahead(1, |t| t.is_ident()) {
 273             self.sess.emit_err(ConstLetMutuallyExclusive { span: lo.to(self.token.span) });
 274             self.bump();
 275         }
 276
 277         self.report_invalid_identifier_error()?;
 278         let (pat, colon) =
 279             self.parse_pat_before_ty(None, RecoverComma::Yes, PatternLocation::LetBinding)?;
 280
 281         let (err, ty) = if colon {
 282             // Save the state of the parser before parsing type normally, in case there is a `:`
 283             // instead of an `=` typo.
 284             let parser_snapshot_before_type = self.clone();
 285             let colon_sp = self.prev_token.span;
 286             match self.parse_ty() {
 287                 Ok(ty) => (None, Some(ty)),
 288                 Err(mut err) => {
 289                     if let Ok(snip) = self.span_to_snippet(pat.span) {
 290                         err.span_label(pat.span, format!("while parsing the type for `{}`", snip));
 291                     }
 292                     // we use noexpect here because we don't actually expect Eq to be here
 293                     // but we are still checking for it in order to be able to handle it if
 294                     // it is there
 295                     let err = if self.check_noexpect(&token::Eq) {
 296                         err.emit();
 297                         None
 298                     } else {
 299                         // Rewind to before attempting to parse the type and continue parsing.
 300                         let parser_snapshot_after_type =
 301                             mem::replace(self, parser_snapshot_before_type);
 302                         Some((parser_snapshot_after_type, colon_sp, err))
 303                     };
 304                     (err, None)
 305                 }
 306             }
 307         } else {
 308             (None, None)
 309         };
 310         let init = match (self.parse_initializer(err.is_some()), err) {
 311             (Ok(init), None) => {
 312                 // init parsed, ty parsed
 313                 init
 314             }
 315             (Ok(init), Some((_, colon_sp, mut err))) => {
 316                 // init parsed, ty error
 317                 // Could parse the type as if it were the initializer, it is likely there was a
 318                 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
 319                 err.span_suggestion_short(
 320                     colon_sp,
 321                     "use `=` if you meant to assign",
 322                     " =",
 323                     Applicability::MachineApplicable,
 324                 );
 325                 err.emit();
 326                 // As this was parsed successfully, continue as if the code has been fixed for the
 327                 // rest of the file. It will still fail due to the emitted error, but we avoid
 328                 // extra noise.
 329                 init
 330             }
 331             (Err(init_err), Some((snapshot, _, ty_err))) => {
 332                 // init error, ty error
 333                 init_err.cancel();
 334                 // Couldn't parse the type nor the initializer, only raise the type error and
 335                 // return to the parser state before parsing the type as the initializer.
 336                 // let x: <parse_error>;
 337                 *self = snapshot;
 338                 return Err(ty_err);
 339             }
 340             (Err(err), None) => {
 341                 // init error, ty parsed
 342                 // Couldn't parse the initializer and we're not attempting to recover a failed
 343                 // parse of the type, return the error.
 344                 return Err(err);
 345             }
 346         };
 347         let kind = match init {
 348             None => LocalKind::Decl,
 349             Some(init) => {
 350                 if self.eat_keyword(kw::Else) {
 351                     if self.token.is_keyword(kw::If) {
 352                         // `let...else if`. Emit the same error that `parse_block()` would,
 353                         // but explicitly point out that this pattern is not allowed.
 354                         let msg = "conditional `else if` is not supported for `let...else`";
 355                         return Err(self.error_block_no_opening_brace_msg(msg));
 356                     }
 357                     let els = self.parse_block()?;
 358                     self.check_let_else_init_bool_expr(&init);
 359                     self.check_let_else_init_trailing_brace(&init);
 360                     LocalKind::InitElse(init, els)
 361                 } else {
 362                     LocalKind::Init(init)
 363                 }
 364             }
 365         };
 366         let hi = if self.token == token::Semi { self.token.span } else { self.prev_token.span };
 367         Ok(P(ast::Local { ty, pat, kind, id: DUMMY_NODE_ID, span: lo.to(hi), attrs, tokens: None }))
 368     }
 369
 370     /// report error for `let 1x = 123`
 371     pub fn report_invalid_identifier_error(&mut self) -> PResult<'a, ()> {
 372         if let token::Literal(lit) = self.token.uninterpolate().kind &&
 373             rustc_ast::MetaItemLit::from_token(&self.token).is_none() &&
 374             (lit.kind == token::LitKind::Integer || lit.kind == token::LitKind::Float) &&
 375             self.look_ahead(1, |t| matches!(t.kind, token::Eq) || matches!(t.kind, token::Colon ) ) {
 376                 return Err(self.sess.create_err(InvalidIdentiferStartsWithNumber { span: self.token.span }));
 377         }
 378         Ok(())
 379     }
 380
 381     fn check_let_else_init_bool_expr(&self, init: &ast::Expr) {
 382         if let ast::ExprKind::Binary(op, ..) = init.kind {
 383             if op.node.lazy() {
 384                 self.sess.emit_err(InvalidExpressionInLetElse {
 385                     span: init.span,
 386                     operator: op.node.to_string(),
 387                     sugg: WrapExpressionInParentheses {
 388                         left: init.span.shrink_to_lo(),
 389                         right: init.span.shrink_to_hi(),
 390                     },
 391                 });
 392             }
 393         }
 394     }
 395
 396     fn check_let_else_init_trailing_brace(&self, init: &ast::Expr) {
 397         if let Some(trailing) = classify::expr_trailing_brace(init) {
 398             self.sess.emit_err(InvalidCurlyInLetElse {
 399                 span: trailing.span.with_lo(trailing.span.hi() - BytePos(1)),
 400                 sugg: WrapExpressionInParentheses {
 401                     left: trailing.span.shrink_to_lo(),
 402                     right: trailing.span.shrink_to_hi(),
 403                 },
 404             });
 405         }
 406     }
 407
 408     /// Parses the RHS of a local variable declaration (e.g., `= 14;`).
 409     fn parse_initializer(&mut self, eq_optional: bool) -> PResult<'a, Option<P<Expr>>> {
 410         let eq_consumed = match self.token.kind {
 411             token::BinOpEq(..) => {
 412                 // Recover `let x <op>= 1` as `let x = 1`
 413                 self.sess.emit_err(CompoundAssignmentExpressionInLet { span: self.token.span });
 414                 self.bump();
 415                 true
 416             }
 417             _ => self.eat(&token::Eq),
 418         };
 419
 420         Ok(if eq_consumed || eq_optional { Some(self.parse_expr()?) } else { None })
 421     }
 422
 423     /// Parses a block. No inner attributes are allowed.
 424     pub(super) fn parse_block(&mut self) -> PResult<'a, P<Block>> {
 425         let (attrs, block) = self.parse_inner_attrs_and_block()?;
 426         if let [.., last] = &*attrs {
 427             self.error_on_forbidden_inner_attr(
 428                 last.span,
 429                 super::attr::InnerAttrPolicy::Forbidden(Some(
 430                     InnerAttrForbiddenReason::InCodeBlock,
 431                 )),
 432             );
 433         }
 434         Ok(block)
 435     }
 436
 437     fn error_block_no_opening_brace_msg(
 438         &mut self,
 439         msg: &str,
 440     ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
 441         let sp = self.token.span;
 442         let mut e = self.struct_span_err(sp, msg);
 443         let do_not_suggest_help = self.token.is_keyword(kw::In) || self.token == token::Colon;
 444
 445         // Check to see if the user has written something like
 446         //
 447         //    if (cond)
 448         //      bar;
 449         //
 450         // which is valid in other languages, but not Rust.
 451         match self.parse_stmt_without_recovery(false, ForceCollect::No) {
 452             // If the next token is an open brace, e.g., we have:
 453             //
 454             //     if expr other_expr {
 455             //        ^    ^          ^- lookahead(1) is a brace
 456             //        |    |- current token is not "else"
 457             //        |- (statement we just parsed)
 458             //
 459             // the place-inside-a-block suggestion would be more likely wrong than right.
 460             //
 461             // FIXME(compiler-errors): this should probably parse an arbitrary expr and not
 462             // just lookahead one token, so we can see if there's a brace after _that_,
 463             // since we want to protect against:
 464             //     `if 1 1 + 1 {` being suggested as  `if { 1 } 1 + 1 {`
 465             //                                            +   +
 466             Ok(Some(_))
 467                 if (!self.token.is_keyword(kw::Else)
 468                     && self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Brace)))
 469                     || do_not_suggest_help => {}
 470             // Do not suggest `if foo println!("") {;}` (as would be seen in test for #46836).
 471             Ok(Some(Stmt { kind: StmtKind::Empty, .. })) => {}
 472             Ok(Some(stmt)) => {
 473                 let stmt_own_line = self.sess.source_map().is_line_before_span_empty(sp);
 474                 let stmt_span = if stmt_own_line && self.eat(&token::Semi) {
 475                     // Expand the span to include the semicolon.
 476                     stmt.span.with_hi(self.prev_token.span.hi())
 477                 } else {
 478                     stmt.span
 479                 };
 480                 e.multipart_suggestion(
 481                     "try placing this code inside a block",
 482                     vec![
 483                         (stmt_span.shrink_to_lo(), "{ ".to_string()),
 484                         (stmt_span.shrink_to_hi(), " }".to_string()),
 485                     ],
 486                     // Speculative; has been misleading in the past (#46836).
 487                     Applicability::MaybeIncorrect,
 488                 );
 489             }
 490             Err(e) => {
 491                 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
 492                 e.cancel();
 493             }
 494             _ => {}
 495         }
 496         e.span_label(sp, "expected `{`");
 497         e
 498     }
 499
 500     fn error_block_no_opening_brace<T>(&mut self) -> PResult<'a, T> {
 501         let tok = super::token_descr(&self.token);
 502         let msg = format!("expected `{{`, found {}", tok);
 503         Err(self.error_block_no_opening_brace_msg(&msg))
 504     }
 505
 506     /// Parses a block. Inner attributes are allowed.
 507     pub(super) fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (AttrVec, P<Block>)> {
 508         self.parse_block_common(self.token.span, BlockCheckMode::Default, true)
 509     }
 510
 511     /// Parses a block. Inner attributes are allowed.
 512     pub(super) fn parse_block_common(
 513         &mut self,
 514         lo: Span,
 515         blk_mode: BlockCheckMode,
 516         can_be_struct_literal: bool,
 517     ) -> PResult<'a, (AttrVec, P<Block>)> {
 518         maybe_whole!(self, NtBlock, |x| (AttrVec::new(), x));
 519
 520         let maybe_ident = self.prev_token.clone();
 521         self.maybe_recover_unexpected_block_label();
 522         if !self.eat(&token::OpenDelim(Delimiter::Brace)) {
 523             return self.error_block_no_opening_brace();
 524         }
 525
 526         let attrs = self.parse_inner_attributes()?;
 527         let tail = match self.maybe_suggest_struct_literal(
 528             lo,
 529             blk_mode,
 530             maybe_ident,
 531             can_be_struct_literal,
 532         ) {
 533             Some(tail) => tail?,
 534             None => self.parse_block_tail(lo, blk_mode, AttemptLocalParseRecovery::Yes)?,
 535         };
 536         Ok((attrs, tail))
 537     }
 538
 539     /// Parses the rest of a block expression or function body.
 540     /// Precondition: already parsed the '{'.
 541     pub(crate) fn parse_block_tail(
 542         &mut self,
 543         lo: Span,
 544         s: BlockCheckMode,
 545         recover: AttemptLocalParseRecovery,
 546     ) -> PResult<'a, P<Block>> {
 547         let mut stmts = vec![];
 548         let mut snapshot = None;
 549         while !self.eat(&token::CloseDelim(Delimiter::Brace)) {
 550             if self.token == token::Eof {
 551                 break;
 552             }
 553             if self.is_diff_marker(&TokenKind::BinOp(token::Shl), &TokenKind::Lt) {
 554                 // Account for `<<<<<<<` diff markers. We can't proactively error here because
 555                 // that can be a valid path start, so we snapshot and reparse only we've
 556                 // encountered another parse error.
 557                 snapshot = Some(self.create_snapshot_for_diagnostic());
 558             }
 559             let stmt = match self.parse_full_stmt(recover) {
 560                 Err(mut err) if recover.yes() => {
 561                     self.maybe_annotate_with_ascription(&mut err, false);
 562                     if let Some(ref mut snapshot) = snapshot {
 563                         snapshot.recover_diff_marker();
 564                     }
 565                     err.emit();
 566                     self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
 567                     Some(self.mk_stmt_err(self.token.span))
 568                 }
 569                 Ok(stmt) => stmt,
 570                 Err(err) => return Err(err),
 571             };
 572             if let Some(stmt) = stmt {
 573                 stmts.push(stmt);
 574             } else {
 575                 // Found only `;` or `}`.
 576                 continue;
 577             };
 578         }
 579         Ok(self.mk_block(stmts, s, lo.to(self.prev_token.span)))
 580     }
 581
 582     /// Parses a statement, including the trailing semicolon.
 583     pub fn parse_full_stmt(
 584         &mut self,
 585         recover: AttemptLocalParseRecovery,
 586     ) -> PResult<'a, Option<Stmt>> {
 587         // Skip looking for a trailing semicolon when we have an interpolated statement.
 588         maybe_whole!(self, NtStmt, |x| Some(x.into_inner()));
 589
 590         let Some(mut stmt) = self.parse_stmt_without_recovery(true, ForceCollect::No)? else {
 591             return Ok(None);
 592         };
 593
 594         let mut eat_semi = true;
 595         match &mut stmt.kind {
 596             // Expression without semicolon.
 597             StmtKind::Expr(expr)
 598                 if self.token != token::Eof && classify::expr_requires_semi_to_be_stmt(expr) => {
 599                 // Just check for errors and recover; do not eat semicolon yet.
 600                 // `expect_one_of` returns PResult<'a, bool /* recovered */>
 601                 let replace_with_err =
 602                     match self.expect_one_of(&[], &[token::Semi, token::CloseDelim(Delimiter::Brace)]) {
 603                     // Recover from parser, skip type error to avoid extra errors.
 604                     Ok(true) => true,
 605                     Err(mut e) => {
 606                         if let TokenKind::DocComment(..) = self.token.kind &&
 607                             let Ok(snippet) = self.span_to_snippet(self.token.span) {
 608                                 let sp = self.token.span;
 609                                 let marker = &snippet[..3];
 610                                 let (comment_marker, doc_comment_marker) = marker.split_at(2);
 611
 612                                 e.span_suggestion(
 613                                     sp.with_hi(sp.lo() + BytePos(marker.len() as u32)),
 614                                     &format!(
 615                                         "add a space before `{}` to use a regular comment",
 616                                         doc_comment_marker,
 617                                     ),
 618                                     format!("{} {}", comment_marker, doc_comment_marker),
 619                                     Applicability::MaybeIncorrect,
 620                                 );
 621                         }
 622
 623                         if let Err(mut e) =
 624                             self.check_mistyped_turbofish_with_multiple_type_params(e, expr)
 625                         {
 626                             if recover.no() {
 627                                 return Err(e);
 628                             }
 629                             e.emit();
 630                             self.recover_stmt();
 631                         }
 632                         true
 633                     }
 634                     _ => false
 635                 };
 636                 if replace_with_err {
 637                     // We already emitted an error, so don't emit another type error
 638                     let sp = expr.span.to(self.prev_token.span);
 639                     *expr = self.mk_expr_err(sp);
 640                 }
 641             }
 642             StmtKind::Expr(_) | StmtKind::MacCall(_) => {}
 643             StmtKind::Local(local) if let Err(e) = self.expect_semi() => {
 644                 // We might be at the `,` in `let x = foo<bar, baz>;`. Try to recover.
 645                 match &mut local.kind {
 646                     LocalKind::Init(expr) | LocalKind::InitElse(expr, _) => {
 647                         self.check_mistyped_turbofish_with_multiple_type_params(e, expr)?;
 648                         // We found `foo<bar, baz>`, have we fully recovered?
 649                         self.expect_semi()?;
 650                     }
 651                     LocalKind::Decl => return Err(e),
 652                 }
 653                 eat_semi = false;
 654             }
 655             StmtKind::Empty | StmtKind::Item(_) | StmtKind::Local(_) | StmtKind::Semi(_) => eat_semi = false,
 656         }
 657
 658         if eat_semi && self.eat(&token::Semi) {
 659             stmt = stmt.add_trailing_semicolon();
 660         }
 661         stmt.span = stmt.span.to(self.prev_token.span);
 662         Ok(Some(stmt))
 663     }
 664
 665     pub(super) fn mk_block(&self, stmts: Vec<Stmt>, rules: BlockCheckMode, span: Span) -> P<Block> {
 666         P(Block {
 667             stmts,
 668             id: DUMMY_NODE_ID,
 669             rules,
 670             span,
 671             tokens: None,
 672             could_be_bare_literal: false,
 673         })
 674     }
 675
 676     pub(super) fn mk_stmt(&self, span: Span, kind: StmtKind) -> Stmt {
 677         Stmt { id: DUMMY_NODE_ID, kind, span }
 678     }
 679
 680     pub(super) fn mk_stmt_err(&self, span: Span) -> Stmt {
 681         self.mk_stmt(span, StmtKind::Expr(self.mk_expr_err(span)))
 682     }
 683
 684     pub(super) fn mk_block_err(&self, span: Span) -> P<Block> {
 685         self.mk_block(vec![self.mk_stmt_err(span)], BlockCheckMode::Default, span)
 686     }
 687 }