From 7b36408b5f6373647eba37ad1f91c26070298454 Mon Sep 17 00:00:00 2001 From: Aaron Hill Date: Fri, 8 Jan 2021 18:16:20 -0500 Subject: [PATCH] Use an empty `TokenCursorFrame` stack when capturing tokens We will never need to pop past our starting frame during token capturing. Using an empty stack allows us to avoid pointless heap allocations/deallocations. --- compiler/rustc_parse/src/parser/mod.rs | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs index 073e62c41d311..cecf0130cf7db 100644 --- a/compiler/rustc_parse/src/parser/mod.rs +++ b/compiler/rustc_parse/src/parser/mod.rs @@ -1239,7 +1239,15 @@ impl<'a> Parser<'a> { f: impl FnOnce(&mut Self) -> PResult<'a, R>, ) -> PResult<'a, (R, Option)> { let start_token = (self.token.clone(), self.token_spacing); - let cursor_snapshot = self.token_cursor.clone(); + let cursor_snapshot = TokenCursor { + frame: self.token_cursor.frame.clone(), + // We only ever capture tokens within our current frame, + // so we can just use an empty frame stack + stack: vec![], + desugar_doc_comments: self.token_cursor.desugar_doc_comments, + num_next_calls: self.token_cursor.num_next_calls, + append_unglued_token: self.token_cursor.append_unglued_token.clone(), + }; let ret = f(self)?;