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sheaf authored
fixes #9192 and #17126 updates containers submodule 1. Changes the type of the primop `reallyUnsafePtrEquality#` to the most general version possible (heterogeneous as well as levity-polymorphic): > reallyUnsafePtrEquality# > :: forall {l :: Levity} {k :: Levity} > (a :: TYPE (BoxedRep l)) (b :: TYPE (BoxedRep k)) > . a -> b -> Int# 2. Adds a new internal module, `GHC.Ext.PtrEq`, which contains pointer equality operations that are now subsumed by `reallyUnsafePtrEquality#`. These functions are then re-exported by `GHC.Exts` (so that no function goes missing from the export list of `GHC.Exts`, which is user-facing). More specifically, `GHC.Ext.PtrEq` defines: - A new function: * reallyUnsafePtrEquality :: forall (a :: Type). a -> a -> Int# - Library definitions of ex-primops: * `sameMutableArray#` * `sameSmallMutableArray` * `sameMutableByteArray#` * `sameMutableArrayArray#` * `sameMutVar#` * `sameTVar#` * `sameMVar#` * `sameIOPort#` * `eqStableName#` - New functions for comparing non-mutable arrays: * `sameArray#` * `sameSmallArray#` * `sameByteArray#` * `sameArrayArray#` These were requested in #9192. Generally speaking, existing libraries that use `reallyUnsafePtrEquality#` will continue to work with the new, levity-polymorphic version. But not all! Some (`containers`, `unordered-containers`, `dependent-map`) contain the following: > unsafeCoerce# reallyUnsafePtrEquality# a b If we make `reallyUnsafePtrEquality#` levity-polymorphic, this code fails the current GHC representation-polymorphism checks. We agreed that the right solution here is to modify the library; in this case by deleting the call to `unsafeCoerce#`, since `reallyUnsafePtrEquality#` is now type-heterogeneous too.
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