Auto merge of #80830 - Aaron1011:capture-token-empty-stack, r=petrochenkov

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.
This commit is contained in:
bors 2021-01-09 19:33:23 +00:00
commit 6184f23950

View File

@ -1239,7 +1239,15 @@ impl<'a> Parser<'a> {
f: impl FnOnce(&mut Self) -> PResult<'a, R>,
) -> PResult<'a, (R, Option<LazyTokenStream>)> {
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)?;