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Auto merge of #113270 - the8472:opt-macro-tts, r=nnethercote

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perform TokenStream replacement in-place when possible in expand_macro
This commit is contained in:
bors 2023-07-07 08:04:48 +00:00
commit 921f669749
2 changed files with 13 additions and 5 deletions
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15
compiler/rustc_ast/src/tokenstream.rs
View file

@ -25,7 +25,7 @@ use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
use rustc_span::{Span, DUMMY_SP};
use smallvec::{smallvec, SmallVec};
use std::{fmt, iter};
use std::{fmt, iter, mem};
/// When the main Rust parser encounters a syntax-extension invocation, it
/// parses the arguments to the invocation as a token tree. This is a very
@ -410,8 +410,17 @@ impl TokenStream {
t1.next().is_none() && t2.next().is_none()
}
pub fn map_enumerated<F: FnMut(usize, &TokenTree) -> TokenTree>(self, mut f: F) -> TokenStream {
TokenStream(Lrc::new(self.0.iter().enumerate().map(|(i, tree)| f(i, tree)).collect()))
/// Applies the supplied function to each `TokenTree` and its index in `self`, returning a new `TokenStream`
///
/// It is equivalent to `TokenStream::new(self.trees().cloned().enumerate().map(|(i, tt)| f(i, tt)).collect())`.
pub fn map_enumerated_owned(
mut self,
mut f: impl FnMut(usize, TokenTree) -> TokenTree,
) -> TokenStream {
let owned = Lrc::make_mut(&mut self.0); // clone if necessary
// rely on vec's in-place optimizations to avoid another allocation
*owned = mem::take(owned).into_iter().enumerate().map(|(i, tree)| f(i, tree)).collect();
self
}
/// Create a token stream containing a single token with alone spacing.

3
compiler/rustc_expand/src/mbe/macro_rules.rs
View file

@ -223,8 +223,7 @@ fn expand_macro<'cx>(
// Replace all the tokens for the corresponding positions in the macro, to maintain
// proper positions in error reporting, while maintaining the macro_backtrace.
if tts.len() == rhs.tts.len() {
tts = tts.map_enumerated(|i, tt| {
let mut tt = tt.clone();
tts = tts.map_enumerated_owned(|i, mut tt| {
let rhs_tt = &rhs.tts[i];
let ctxt = tt.span().ctxt();
match (&mut tt, rhs_tt) {