CoAlloc: Vec: COOP_PREFERRED

Author: peter-lyons-kehl

library/alloc/src/vec/into_iter.rs

@@ -131,7 +131,17 @@ where
         // struct and then overwriting &mut self.
         // this creates less assembly
         self.cap = 0;
-        self.buf = unsafe { NonNull::new_unchecked(RawVec::NEW.ptr()) };
+        self.buf = unsafe {
+            // @FIXME The below if COOP_PREFERRED {..} else {..}
+            // branching exists, because the following fails. Otherwise we'd have a snowball effect of wide spread of where...Global...
+            //
+            // NonNull::new_unchecked(RawVec::<T, Global, COOP_PREFERRED>::NEW.ptr())
+            if COOP_PREFERRED {
+                NonNull::new_unchecked(RawVec::<T, Global, true>::NEW.ptr())
+            } else {
+                NonNull::new_unchecked(RawVec::<T, Global, false>::NEW.ptr())
+            }
+        };
         self.ptr = self.buf.as_ptr();
         self.end = self.buf.as_ptr();
 

library/alloc/src/vec/splice.rs

@@ -115,9 +115,9 @@ where
 }
 
 /// Private helper methods for `Splice::drop`
-impl<T, A: Allocator> Drain<'_, T, A>
+impl<T, A: Allocator, const COOP_PREFERRED: bool> Drain<'_, T, A, COOP_PREFERRED>
 where
-    [(); alloc::co_alloc_metadata_num_slots_with_preference::<A>(true)]:,
+    [(); alloc::co_alloc_metadata_num_slots_with_preference::<A>(COOP_PREFERRED)]:,
 {
     /// The range from `self.vec.len` to `self.tail_start` contains elements
     /// that have been moved out.