CoAlloc: Vec: Fixing COOP_PREFERRED.

Author: peter-lyons-kehl

library/alloc/src/vec/in_place_collect.rs

@@ -137,13 +137,11 @@
 //! }
 //! vec.truncate(write_idx);
 //! ```
+use core::alloc::{self, Allocator};
 use core::iter::{InPlaceIterable, SourceIter, TrustedRandomAccessNoCoerce};
 use core::mem::{self, ManuallyDrop, SizedTypeProperties};
 use core::ptr::{self};
 
-use crate::Global;
-use crate::DEFAULT_COOP_PREFERRED;
-
 use super::{InPlaceDrop, InPlaceDstBufDrop, SpecFromIter, SpecFromIterNested, Vec};
 
 /// Specialization marker for collecting an iterator pipeline into a Vec while reusing the
@@ -154,9 +152,11 @@ pub(super) trait InPlaceIterableMarker {}
 impl<T> InPlaceIterableMarker for T where T: InPlaceIterable {}
 
 #[allow(unused_braces)]
-impl<T, I> SpecFromIter<T, I> for Vec<T, Global, {DEFAULT_COOP_PREFERRED!()}>
+impl<T, I, A: Allocator,  const COOP_PREFERRED: bool> SpecFromIter<T, I> for Vec<T, A, COOP_PREFERRED>
 where
     I: Iterator<Item = T> + SourceIter<Source: AsVecIntoIter> + InPlaceIterableMarker,
+    [(); alloc::co_alloc_metadata_num_slots_with_preference::<A>(COOP_PREFERRED)]:,
+
 {
     default fn from_iter(mut iterator: I) -> Self {
         // See "Layout constraints" section in the module documentation. We rely on const

library/alloc/src/vec/spec_from_iter.rs

@@ -1,7 +1,6 @@
+use core::alloc::{self, Allocator};
 use core::mem::ManuallyDrop;
 use core::ptr::{self};
-use crate::Global;
-use crate::DEFAULT_COOP_PREFERRED;
 
 use super::{IntoIter, SpecExtend, SpecFromIterNested, Vec};
 
@@ -28,17 +27,21 @@ pub(super) trait SpecFromIter<T, I> {
 }
 
 #[allow(unused_braces)]
-impl<T, I> SpecFromIter<T, I> for Vec<T, Global, {DEFAULT_COOP_PREFERRED!()}>
+impl<T, I, A: Allocator, const COOP_PREFERRED: bool> SpecFromIter<T, I> for Vec<T, A, COOP_PREFERRED>
 where
     I: Iterator<Item = T>,
+    [(); alloc::co_alloc_metadata_num_slots_with_preference::<A>(COOP_PREFERRED)]:,
 {
     default fn from_iter(iterator: I) -> Self {
         SpecFromIterNested::from_iter(iterator)
     }
 }
 
 #[allow(unused_braces)]
-impl<T> SpecFromIter<T, IntoIter<T>> for Vec<T,  Global, {DEFAULT_COOP_PREFERRED!()}> {
+impl<T, A: Allocator, const COOP_PREFERRED: bool> SpecFromIter<T, IntoIter<T>> for Vec<T, A, COOP_PREFERRED>
+where
+[(); alloc::co_alloc_metadata_num_slots_with_preference::<A>(COOP_PREFERRED)]:,
+{
     fn from_iter(iterator: IntoIter<T>) -> Self {
         // A common case is passing a vector into a function which immediately
         // re-collects into a vector. We can short circuit this if the IntoIter