Type family not reduced
Andres pointed out that the following fails to compile with GHC 8.0.1 but succeeds with master
(f53d761d),
{-# LANGUAGE TypeInType, TypeFamilies #-}
module Kinds where
import GHC.Types
type family G (a :: Type) :: Type
type instance G Int = Bool
type family F (a :: Type) :: G a
type instance F Int = True
Error:
Hi.hs:10:23: error:
• Expected kind ‘G Int’, but ‘'True’ has kind ‘Bool’
• In the type ‘True’
In the type instance declaration for ‘F’
We should figure out what fixed this so it can hopefully be merged for 8.0.2. I initially suspected the patch cited in #12175 (closed) but sadly this doesn't seem to be the case.
Trac metadata
Trac field | Value |
---|---|
Version | 8.0.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |