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Remove TokenStream::from_streams.

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By inlining it into the only non-test call site. The one test call site
is changed to use `TokenStreamBuilder`.
This commit is contained in:
Nicholas Nethercote 2022-06-20 09:33:08 +10:00
parent 178b746d04
commit f6b57883e0
2 changed files with 41 additions and 42 deletions
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77
compiler/rustc_ast/src/tokenstream.rs
View file

@ -399,45 +399,6 @@ impl TokenStream {
self.0.len()
}
pub fn from_streams(mut streams: SmallVec<[TokenStream; 2]>) -> TokenStream {
match streams.len() {
0 => TokenStream::default(),
1 => streams.pop().unwrap(),
_ => {
// We are going to extend the first stream in `streams` with
// the elements from the subsequent streams. This requires
// using `make_mut()` on the first stream, and in practice this
// doesn't cause cloning 99.9% of the time.
//
// One very common use case is when `streams` has two elements,
// where the first stream has any number of elements within
// (often 1, but sometimes many more) and the second stream has
// a single element within.
// Determine how much the first stream will be extended.
// Needed to avoid quadratic blow up from on-the-fly
// reallocations (#57735).
let num_appends = streams.iter().skip(1).map(|ts| ts.len()).sum();
// Get the first stream. If it's `None`, create an empty
// stream.
let mut iter = streams.drain(..);
let mut first_stream_lrc = iter.next().unwrap().0;
// Append the elements to the first stream, after reserving
// space for them.
let first_vec_mut = Lrc::make_mut(&mut first_stream_lrc);
first_vec_mut.reserve(num_appends);
for stream in iter {
first_vec_mut.extend(stream.0.iter().cloned());
}
// Create the final `TokenStream`.
TokenStream(first_stream_lrc)
}
}
}
pub fn trees(&self) -> CursorRef<'_> {
CursorRef::new(self)
}
@ -605,7 +566,43 @@ impl TokenStreamBuilder {
}
pub fn build(self) -> TokenStream {
TokenStream::from_streams(self.0)
let mut streams = self.0;
match streams.len() {
0 => TokenStream::default(),
1 => streams.pop().unwrap(),
_ => {
// We are going to extend the first stream in `streams` with
// the elements from the subsequent streams. This requires
// using `make_mut()` on the first stream, and in practice this
// doesn't cause cloning 99.9% of the time.
//
// One very common use case is when `streams` has two elements,
// where the first stream has any number of elements within
// (often 1, but sometimes many more) and the second stream has
// a single element within.
// Determine how much the first stream will be extended.
// Needed to avoid quadratic blow up from on-the-fly
// reallocations (#57735).
let num_appends = streams.iter().skip(1).map(|ts| ts.len()).sum();
// Get the first stream. If it's `None`, create an empty
// stream.
let mut iter = streams.drain(..);
let mut first_stream_lrc = iter.next().unwrap().0;
// Append the elements to the first stream, after reserving
// space for them.
let first_vec_mut = Lrc::make_mut(&mut first_stream_lrc);
first_vec_mut.reserve(num_appends);
for stream in iter {
first_vec_mut.extend(stream.0.iter().cloned());
}
// Create the final `TokenStream`.
TokenStream(first_stream_lrc)
}
}
}
}

6
compiler/rustc_expand/src/tokenstream/tests.rs
View file

@ -4,7 +4,6 @@ use rustc_ast::token;
use rustc_ast::tokenstream::{Spacing, TokenStream, TokenStreamBuilder, TokenTree};
use rustc_span::create_default_session_globals_then;
use rustc_span::{BytePos, Span, Symbol};
use smallvec::smallvec;
fn string_to_ts(string: &str) -> TokenStream {
string_to_stream(string.to_owned())
@ -24,7 +23,10 @@ fn test_concat() {
let test_res = string_to_ts("foo::bar::baz");
let test_fst = string_to_ts("foo::bar");
let test_snd = string_to_ts("::baz");
let eq_res = TokenStream::from_streams(smallvec![test_fst, test_snd]);
let mut builder = TokenStreamBuilder::new();
builder.push(test_fst);
builder.push(test_snd);
let eq_res = builder.build();
assert_eq!(test_res.trees().count(), 5);
assert_eq!(eq_res.trees().count(), 5);
assert_eq!(test_res.eq_unspanned(&eq_res), true);