Add benchmark of parsing whole rust repo

On my machine:

    tokenstream_parse:  elapsed=1.453s
    syn_parse:          elapsed=4.632s
    libsyntax_parse:    elapsed=2.039s

3 files changed, 112 insertions, 1 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 1ca12ee9..a394b8d2 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -43,6 +43,12 @@ regex = "1.0"
 termcolor = "1.0"
 walkdir = "2.1"
 
+[[bench]]
+name = "rust"
+edition = "2018"
+harness = false
+required-features = ["full", "parsing"]
+
 [package.metadata.docs.rs]
 all-features = true
 
diff --git a/benches/rust.rs b/benches/rust.rs
new file mode 100644
index 00000000..2a5005e8
--- /dev/null
+++ b/benches/rust.rs
@@ -0,0 +1,106 @@
+// $ cargo bench --features full
+
+#![recursion_limit = "256"]
+#![feature(rustc_private)]
+
+extern crate rustc_data_structures;
+extern crate syntax;
+extern crate syntax_pos;
+
+#[macro_use]
+#[path = "../tests/macros/mod.rs"]
+mod macros;
+
+#[path = "../tests/common/mod.rs"]
+mod common;
+
+use proc_macro2::TokenStream;
+use rustc_data_structures::sync::Lrc;
+use std::str::FromStr;
+use std::time::{Duration, Instant};
+use syntax::edition::Edition;
+use syntax::errors::{emitter::Emitter, DiagnosticBuilder, Handler};
+use syntax::parse::ParseSess;
+use syntax::source_map::{FilePathMapping, SourceMap};
+use syntax_pos::FileName;
+
+fn tokenstream_parse(content: &str) -> Result<(), ()> {
+    TokenStream::from_str(content).map(drop).map_err(drop)
+}
+
+fn syn_parse(content: &str) -> Result<(), ()> {
+    syn::parse_file(content).map(drop).map_err(drop)
+}
+
+fn libsyntax_parse(content: &str) -> Result<(), ()> {
+    struct SilentEmitter;
+
+    impl Emitter for SilentEmitter {
+        fn emit_diagnostic(&mut self, _db: &DiagnosticBuilder) {}
+    }
+
+    syntax::with_globals(Edition::Edition2018, || {
+        let cm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let emitter = Box::new(SilentEmitter);
+        let handler = Handler::with_emitter(false, None, emitter);
+        let sess = ParseSess::with_span_handler(handler, cm);
+        if let Err(mut diagnostic) = syntax::parse::parse_crate_from_source_str(
+            FileName::Custom("bench".to_owned()),
+            content.to_owned(),
+            &sess,
+        ) {
+            diagnostic.cancel();
+            return Err(());
+        };
+        Ok(())
+    })
+}
+
+fn exec(codepath: fn(&str) -> Result<(), ()>) -> Duration {
+    let begin = Instant::now();
+    let mut success = 0;
+    let mut total = 0;
+
+    walkdir::WalkDir::new("tests/rust/src")
+        .into_iter()
+        .filter_entry(common::base_dir_filter)
+        .for_each(|entry| {
+            let entry = entry.unwrap();
+            let path = entry.path();
+            if path.is_dir() {
+                return;
+            }
+            let content = std::fs::read_to_string(path).unwrap();
+            let ok = codepath(&content).is_ok();
+            success += ok as usize;
+            total += 1;
+            if !ok {
+                eprintln!("FAIL {}", path.display());
+            }
+        });
+
+    assert_eq!(success, total);
+    begin.elapsed()
+}
+
+fn main() {
+    common::clone_rust();
+
+    macro_rules! testcases {
+        ($($name:ident),*) => {
+            vec![
+                $(
+                    (stringify!($name), $name as fn(&str) -> Result<(), ()>),
+                )*
+            ]
+        };
+    }
+
+    eprintln!();
+    for (name, f) in testcases!(tokenstream_parse, syn_parse, libsyntax_parse) {
+        eprint!("{:20}", format!("{}:", name));
+        let elapsed = exec(f);
+        eprintln!("elapsed={}.{:03}s", elapsed.as_secs(), elapsed.subsec_millis());
+    }
+    eprintln!();
+}
diff --git a/tests/common/mod.rs b/tests/common/mod.rs
index c066510c..84b317a4 100644
--- a/tests/common/mod.rs
+++ b/tests/common/mod.rs
@@ -66,6 +66,5 @@ pub fn base_dir_filter(entry: &DirEntry) -> bool {
 
 pub fn clone_rust() {
     let result = Command::new("tests/clone.sh").status().unwrap();
-    println!("result: {}", result);
     assert!(result.success());
 }