1 files changed, 55 insertions, 0 deletions
diff --git a/third_party/rust/syn/benches/file.rs b/third_party/rust/syn/benches/file.rs
new file mode 100644
index 0000000000..bd4a247df6
--- /dev/null
+++ b/third_party/rust/syn/benches/file.rs
@@ -0,0 +1,55 @@
+// $ cargo bench --features full,test --bench file
+
+#![feature(rustc_private, test)]
+#![recursion_limit = "1024"]
+#![allow(
+    clippy::items_after_statements,
+    clippy::missing_panics_doc,
+    clippy::must_use_candidate
+)]
+
+extern crate test;
+
+#[macro_use]
+#[path = "../tests/macros/mod.rs"]
+mod macros;
+
+#[path = "../tests/common/mod.rs"]
+mod common;
+#[path = "../tests/repo/mod.rs"]
+pub mod repo;
+
+use proc_macro2::{Span, TokenStream};
+use std::fs;
+use std::str::FromStr;
+use syn::parse::{ParseStream, Parser};
+use test::Bencher;
+
+const FILE: &str = "tests/rust/library/core/src/str/mod.rs";
+
+fn get_tokens() -> TokenStream {
+    repo::clone_rust();
+    let content = fs::read_to_string(FILE).unwrap();
+    TokenStream::from_str(&content).unwrap()
+}
+
+#[bench]
+fn baseline(b: &mut Bencher) {
+    let tokens = get_tokens();
+    b.iter(|| drop(tokens.clone()));
+}
+
+#[bench]
+fn create_token_buffer(b: &mut Bencher) {
+    let tokens = get_tokens();
+    fn immediate_fail(_input: ParseStream) -> syn::Result<()> {
+        Err(syn::Error::new(Span::call_site(), ""))
+    }
+    b.iter(|| immediate_fail.parse2(tokens.clone()));
+}
+
+#[bench]
+fn parse_file(b: &mut Bencher) {
+    let tokens = get_tokens();
+    b.iter(|| syn::parse2::<syn::File>(tokens.clone()));
+}