Allow kinds of associated types to depend on earlier associated types

GHC rejects the following code:

class C t where
    type K t :: Type
    type T t :: K t -> Type

    m :: t -> T t a

with this error message

    • Type constructor ‘K’ cannot be used here
        (it is defined and used in the same recursive group)
    • In the kind ‘K t -> Type’

See e-mail discussion. This is connected to #12088 (closed), at least as far as defining instances of C.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
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Operating system
Architecture