Merge #4489

4489: Memory allocation optimization r=matklad a=simonvandel

I did some profiling using DHAT, and this was what I could easily optimize without much knowledge of the codebase.

This speeds up analysis-stats on rust-analyser by ~4% on my local machine.

**Benchmark**
➜  rust-analyzer-base git:(master) hyperfine --min-runs=2 '/home/simon/Documents/rust-analyzer/target/release/rust-analyzer analysis-stats .' '/home/simon/Documents/rust-analyzer-base/target/release/rust-analyzer analysis-stats .'
Benchmark #1: /home/simon/Documents/rust-analyzer/target/release/rust-analyzer analysis-stats .
  Time (mean ± σ):     49.621 s ±  0.317 s    [User: 48.725 s, System: 0.792 s]
  Range (min … max):   49.397 s … 49.846 s    2 runs
 
Benchmark #2: /home/simon/Documents/rust-analyzer-base/target/release/rust-analyzer analysis-stats .
  Time (mean ± σ):     51.764 s ±  0.045 s    [User: 50.882 s, System: 0.756 s]
  Range (min … max):   51.733 s … 51.796 s    2 runs
 
Summary
  '/home/simon/Documents/rust-analyzer/target/release/rust-analyzer analysis-stats .' ran
    1.04 ± 0.01 times faster than '/home/simon/Documents/rust-analyzer-base/target/release/rust-analyzer analysis-stats .'

Co-authored-by: Simon Vandel Sillesen <[email protected]>

2 files changed, 2 insertions, 2 deletions

diff --git a/crates/ra_parser/src/lib.rs b/crates/ra_parser/src/lib.rs
index e08ad4dae..eeb8ad66b 100644
--- a/crates/ra_parser/src/lib.rs
+++ b/crates/ra_parser/src/lib.rs
@@ -25,7 +25,7 @@ pub(crate) use token_set::TokenSet;
 pub use syntax_kind::SyntaxKind;
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct ParseError(pub String);
+pub struct ParseError(pub Box<String>);
 
 /// `TokenSource` abstracts the source of the tokens parser operates on.
 ///
diff --git a/crates/ra_parser/src/parser.rs b/crates/ra_parser/src/parser.rs
index faa63d53f..4f59b0a23 100644
--- a/crates/ra_parser/src/parser.rs
+++ b/crates/ra_parser/src/parser.rs
@@ -192,7 +192,7 @@ impl<'t> Parser<'t> {
     /// structured errors with spans and notes, like rustc
     /// does.
     pub(crate) fn error<T: Into<String>>(&mut self, message: T) {
-        let msg = ParseError(message.into());
+        let msg = ParseError(Box::new(message.into()));
         self.push_event(Event::Error { msg })
     }