chore: add vendor dependencies for kauma build

vendor/syn/tests/test_unparenthesize.rs

@@ -0,0 +1,63 @@
+#![cfg(not(miri))]
+#![allow(clippy::manual_assert, clippy::uninlined_format_args)]
+
+use quote::ToTokens as _;
+use std::fs;
+use std::mem;
+use std::panic;
+use std::path::Path;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use syn::visit_mut::{self, VisitMut};
+use syn::Expr;
+
+#[macro_use]
+mod macros;
+
+mod repo;
+
+#[test]
+fn test_unparenthesize() {
+    repo::rayon_init();
+    repo::clone_rust();
+
+    let failed = AtomicUsize::new(0);
+
+    repo::for_each_rust_file(|path| test(path, &failed));
+
+    let failed = failed.into_inner();
+    if failed > 0 {
+        panic!("{} failures", failed);
+    }
+}
+
+struct FlattenParens;
+
+impl VisitMut for FlattenParens {
+    fn visit_expr_mut(&mut self, e: &mut Expr) {
+        while let Expr::Paren(paren) = e {
+            *e = mem::replace(&mut *paren.expr, Expr::PLACEHOLDER);
+        }
+        visit_mut::visit_expr_mut(self, e);
+    }
+}
+
+fn test(path: &Path, failed: &AtomicUsize) {
+    let content = fs::read_to_string(path).unwrap();
+
+    match panic::catch_unwind(|| -> syn::Result<()> {
+        let mut syntax_tree = syn::parse_file(&content)?;
+        FlattenParens.visit_file_mut(&mut syntax_tree);
+        syn::parse2::<syn::File>(syntax_tree.to_token_stream())?;
+        Ok(())
+    }) {
+        Err(_) => {
+            errorf!("=== {}: syn panic\n", path.display());
+            failed.fetch_add(1, Ordering::Relaxed);
+        }
+        Ok(Err(msg)) => {
+            errorf!("=== {}: syn failed to parse\n{:?}\n", path.display(), msg);
+            failed.fetch_add(1, Ordering::Relaxed);
+        }
+        Ok(Ok(())) => {}
+    }
+}