Unbound kind variable can appear in RHS of associated type
Consider the following code:
{-# LANGUAGE TypeFamilies, PolyKinds, MultiParamTypeClasses,
FlexibleInstances, DataKinds #-}
data KProxy (a :: *) = KP
class Foo (a :: k1) (b :: k2) where
type Bar a
instance Foo (a :: k1) (b :: k2) where
type Bar a = (KP :: KProxy k2)The kind variable k2 appears on the RHS of the instance for Bar but not on the left-hand side. This is disallowed for type variables, but there seems to be no check for kind variables.
I will fix in an upcoming patch.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 7.6.3 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |