move retain_unordered_mut function into parallel module

src/lib.rs

@@ -1375,7 +1375,7 @@ impl Build {
 
                 cell_update(&pendings, |mut pendings| {
                     // Try waiting on them.
-                    retain_unordered_mut(&mut pendings, |(cmd, program, child, _token)| {
+                    parallel::retain_unordered_mut(&mut pendings, |(cmd, program, child, _token)| {
                         match try_wait_on_child(cmd, program, &mut child.0, &mut stdout) {
                             Ok(Some(())) => {
                                 // Task done, remove the entry
@@ -4344,21 +4344,3 @@ impl Drop for PrintThread {
         self.handle.take().unwrap().join().unwrap();
     }
 }
-
-/// Remove all element in `vec` which `f(element)` returns `false`.
-///
-/// TODO: Remove this once the MSRV is bumped to v1.61
-#[cfg(feature = "parallel")]
-fn retain_unordered_mut<T, F>(vec: &mut Vec<T>, mut f: F)
-where
-    F: FnMut(&mut T) -> bool,
-{
-    let mut i = 0;
-    while i < vec.len() {
-        if f(&mut vec[i]) {
-            i += 1;
-        } else {
-            vec.swap_remove(i);
-        }
-    }
-}

src/parallel/mod.rs

@@ -1,2 +1,19 @@
 pub(crate) mod async_executor;
 pub(crate) mod job_token;
+
+/// Remove all element in `vec` which `f(element)` returns `false`.
+///
+/// TODO: Remove this once the MSRV is bumped to v1.61
+pub(crate) fn retain_unordered_mut<T, F>(vec: &mut Vec<T>, mut f: F)
+where
+F: FnMut(&mut T) -> bool,
+{
+    let mut i = 0;
+    while i < vec.len() {
+        if f(&mut vec[i]) {
+            i += 1;
+        } else {
+            vec.swap_remove(i);
+        }
+    }
+}