Dyn erase at call site

2 files changed, 12 insertions, 21 deletions

diff --git a/library/std/src/sys/pal/common/small_c_string.rs b/library/std/src/sys/pal/common/small_c_string.rs
index 8e5ecdea9a8..37812fc0659 100644
--- a/library/std/src/sys/pal/common/small_c_string.rs
+++ b/library/std/src/sys/pal/common/small_c_string.rs
@@ -15,24 +15,18 @@ const NUL_ERR: io::Error =
     io::const_io_error!(io::ErrorKind::InvalidInput, "file name contained an unexpected NUL byte");
 
 #[inline]
-pub fn run_path_with_cstr<T, F>(path: &Path, f: F) -> io::Result<T>
-where
-    F: FnMut(&CStr) -> io::Result<T>,
-{
+pub fn run_path_with_cstr<T>(path: &Path, f: &dyn Fn(&CStr) -> io::Result<T>) -> io::Result<T> {
     run_with_cstr(path.as_os_str().as_encoded_bytes(), f)
 }
 
 #[inline]
-pub fn run_with_cstr<T, F>(bytes: &[u8], mut f: F) -> io::Result<T>
-where
-    F: FnMut(&CStr) -> io::Result<T>,
-{
+pub fn run_with_cstr<T>(bytes: &[u8], f: &dyn Fn(&CStr) -> io::Result<T>) -> io::Result<T> {
     // Dispatch and dyn erase the closure type to prevent mono bloat.
     // See https://github.com/rust-lang/rust/pull/121101.
     if bytes.len() >= MAX_STACK_ALLOCATION {
-        run_with_cstr_allocating(bytes, &mut f)
+        run_with_cstr_allocating(bytes, f)
     } else {
-        unsafe { run_with_cstr_stack(bytes, &mut f) }
+        unsafe { run_with_cstr_stack(bytes, f) }
     }
 }
 
@@ -41,7 +35,7 @@ where
 /// `bytes` must have a length less than `MAX_STACK_ALLOCATION`.
 unsafe fn run_with_cstr_stack<T>(
     bytes: &[u8],
-    f: &mut dyn FnMut(&CStr) -> io::Result<T>,
+    f: &dyn Fn(&CStr) -> io::Result<T>,
 ) -> io::Result<T> {
     let mut buf = MaybeUninit::<[u8; MAX_STACK_ALLOCATION]>::uninit();
     let buf_ptr = buf.as_mut_ptr() as *mut u8;
@@ -59,10 +53,7 @@ unsafe fn run_with_cstr_stack<T>(
 
 #[cold]
 #[inline(never)]
-fn run_with_cstr_allocating<T>(
-    bytes: &[u8],
-    f: &mut dyn FnMut(&CStr) -> io::Result<T>,
-) -> io::Result<T> {
+fn run_with_cstr_allocating<T>(bytes: &[u8], f: &dyn Fn(&CStr) -> io::Result<T>) -> io::Result<T> {
     match CString::new(bytes) {
         Ok(s) => f(&s),
         Err(_) => Err(NUL_ERR),
diff --git a/library/std/src/sys/pal/common/tests.rs b/library/std/src/sys/pal/common/tests.rs
index 32dc18ee1cf..e72d02203da 100644
--- a/library/std/src/sys/pal/common/tests.rs
+++ b/library/std/src/sys/pal/common/tests.rs
@@ -7,7 +7,7 @@ use core::iter::repeat;
 #[test]
 fn stack_allocation_works() {
     let path = Path::new("abc");
-    let result = run_path_with_cstr(path, |p| {
+    let result = run_path_with_cstr(path, &|p| {
         assert_eq!(p, &*CString::new(path.as_os_str().as_encoded_bytes()).unwrap());
         Ok(42)
     });
@@ -17,14 +17,14 @@ fn stack_allocation_works() {
 #[test]
 fn stack_allocation_fails() {
     let path = Path::new("ab\0");
-    assert!(run_path_with_cstr::<(), _>(path, |_| unreachable!()).is_err());
+    assert!(run_path_with_cstr::<()>(path, &|_| unreachable!()).is_err());
 }
 
 #[test]
 fn heap_allocation_works() {
     let path = repeat("a").take(384).collect::<String>();
     let path = Path::new(&path);
-    let result = run_path_with_cstr(path, |p| {
+    let result = run_path_with_cstr(path, &|p| {
         assert_eq!(p, &*CString::new(path.as_os_str().as_encoded_bytes()).unwrap());
         Ok(42)
     });
@@ -36,7 +36,7 @@ fn heap_allocation_fails() {
     let mut path = repeat("a").take(384).collect::<String>();
     path.push('\0');
     let path = Path::new(&path);
-    assert!(run_path_with_cstr::<(), _>(path, |_| unreachable!()).is_err());
+    assert!(run_path_with_cstr::<()>(path, &|_| unreachable!()).is_err());
 }
 
 #[bench]
@@ -44,7 +44,7 @@ fn bench_stack_path_alloc(b: &mut test::Bencher) {
     let path = repeat("a").take(383).collect::<String>();
     let p = Path::new(&path);
     b.iter(|| {
-        run_path_with_cstr(p, |cstr| {
+        run_path_with_cstr(p, &|cstr| {
             black_box(cstr);
             Ok(())
         })
@@ -57,7 +57,7 @@ fn bench_heap_path_alloc(b: &mut test::Bencher) {
     let path = repeat("a").take(384).collect::<String>();
     let p = Path::new(&path);
     b.iter(|| {
-        run_path_with_cstr(p, |cstr| {
+        run_path_with_cstr(p, &|cstr| {
             black_box(cstr);
             Ok(())
         })