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Avoid some TokenTree-to-TokenStream conversions.

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This avoids some allocations.
This commit is contained in:
Nicholas Nethercote 2019-01-10 11:58:38 +11:00
parent ce0d9949b8
commit ba31d83adc
1 changed files with 6 additions and 7 deletions
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13
src/libsyntax/parse/parser.rs
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@ -46,7 +46,7 @@ use print::pprust;
use ptr::P;
use parse::PResult;
use ThinVec;
use tokenstream::{self, DelimSpan, TokenTree, TokenStream};
use tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
use symbol::{Symbol, keywords};
use std::borrow::Cow;
@ -280,8 +280,8 @@ struct TokenCursorFrame {
/// on the parser.
#[derive(Clone)]
enum LastToken {
Collecting(Vec<TokenStream>),
Was(Option<TokenStream>),
Collecting(Vec<TreeAndJoint>),
Was(Option<TreeAndJoint>),
}
impl TokenCursorFrame {
@ -7677,7 +7677,7 @@ impl<'a> Parser<'a> {
&mut self.token_cursor.stack[prev].last_token
};
// Pull our the toekns that we've collected from the call to `f` above
// Pull out the tokens that we've collected from the call to `f` above.
let mut collected_tokens = match *last_token {
LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()),
LastToken::Was(_) => panic!("our vector went away?"),
@ -7696,10 +7696,9 @@ impl<'a> Parser<'a> {
// call. In that case we need to record all the tokens we collected in
// our parent list as well. To do that we push a clone of our stream
// onto the previous list.
let stream = collected_tokens.into_iter().collect::<TokenStream>();
match prev_collecting {
Some(mut list) => {
list.push(stream.clone());
list.extend(collected_tokens.iter().cloned());
list.extend(extra_token);
*last_token = LastToken::Collecting(list);
}
@ -7708,7 +7707,7 @@ impl<'a> Parser<'a> {
}
}
Ok((ret?, stream))
Ok((ret?, TokenStream::new(collected_tokens)))
}
pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {