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-rw-r--r--compiler/rustc_ast/src/tokenstream.rs15
1 files changed, 12 insertions, 3 deletions
diff --git a/compiler/rustc_ast/src/tokenstream.rs b/compiler/rustc_ast/src/tokenstream.rs
index db296aa44..ca4a739ab 100644
--- a/compiler/rustc_ast/src/tokenstream.rs
+++ b/compiler/rustc_ast/src/tokenstream.rs
@@ -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.