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
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Operating system
Architecture