Need more kind inference in associated type instances
When I say
{-# LANGUAGE DataKinds, PolyKinds, TypeFamilies #-}
module Bug where
import Data.Proxy
class kproxy ~ 'KProxy => C (kproxy :: KProxy k) where
type F (a :: k)
instance C ('KProxy :: KProxy Bool) where
type F a = Int
I get
Type indexes must match class instance head
Found ‘k’ but expected ‘Bool’
In the type instance declaration for ‘F’
In the instance declaration for ‘C (KProxy :: KProxy Bool)’
But the kind of a
should really be known to be Bool
.
This ticket is broken out from ticket:9063#comment:82569, which was evidently not addressed when fixing that ticket.
Patch coming soon.
Trac metadata
Trac field | Value |
---|---|
Version | 7.10.2 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |