diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs index d64e5173b926c..fe190bfe9d981 100644 --- a/compiler/rustc_parse/src/parser/expr.rs +++ b/compiler/rustc_parse/src/parser/expr.rs @@ -92,6 +92,21 @@ impl<'a> Parser<'a> { self.parse_expr_res(Restrictions::empty(), None) } + /// Parses an expression, forcing tokens to be collected + pub fn parse_expr_force_collect(&mut self) -> PResult<'a, P> { + // If we have outer attributes, then the call to `collect_tokens_trailing_token` + // will be made for us. + if matches!(self.token.kind, TokenKind::Pound | TokenKind::DocComment(..)) { + self.parse_expr() + } else { + // If we don't have outer attributes, then we need to ensure + // that collection happens by using `collect_tokens_no_attrs`. + // Expression don't support custom inner attributes, so `parse_expr` + // will never try to collect tokens if we don't have outer attributes. + self.collect_tokens_no_attrs(|this| this.parse_expr()) + } + } + pub(super) fn parse_anon_const_expr(&mut self) -> PResult<'a, AnonConst> { self.parse_expr().map(|value| AnonConst { id: DUMMY_NODE_ID, value }) } diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs index 71103840f1396..f0ee76d328c40 100644 --- a/compiler/rustc_parse/src/parser/mod.rs +++ b/compiler/rustc_parse/src/parser/mod.rs @@ -987,7 +987,7 @@ impl<'a> Parser<'a> { } // Collect tokens because they are used during lowering to HIR. - let expr = self.collect_tokens_no_attrs(|this| this.parse_expr())?; + let expr = self.parse_expr_force_collect()?; let span = expr.span; match &expr.kind { diff --git a/compiler/rustc_parse/src/parser/nonterminal.rs b/compiler/rustc_parse/src/parser/nonterminal.rs index fc25e883666d1..0c49d10358356 100644 --- a/compiler/rustc_parse/src/parser/nonterminal.rs +++ b/compiler/rustc_parse/src/parser/nonterminal.rs @@ -128,22 +128,7 @@ impl<'a> Parser<'a> { })?) } - // If there are attributes present, then `parse_expr` will end up collecting tokens, - // turning the outer `collect_tokens_no_attrs` into a no-op due to the already present - // tokens. If there are *not* attributes present, then the outer - // `collect_tokens_no_attrs` will ensure that we will end up collecting tokens for the - // expressions. - // - // This is less efficient than it could be, since the outer `collect_tokens_no_attrs` - // still needs to snapshot the `TokenCursor` before calling `parse_expr`, even when - // `parse_expr` will end up collecting tokens. Ideally, this would work more like - // `parse_item`, and take in a `ForceCollect` parameter. However, this would require - // adding a `ForceCollect` parameter in a bunch of places in expression parsing - // for little gain. If the perf impact from this turns out to be noticeable, we should - // revisit this apporach. - NonterminalKind::Expr => { - token::NtExpr(self.collect_tokens_no_attrs(|this| this.parse_expr())?) - } + NonterminalKind::Expr => token::NtExpr(self.parse_expr_force_collect()?), NonterminalKind::Literal => { // The `:literal` matcher does not support attributes token::NtLiteral(