GADTs don't seem to unpack properly

Consider this simple code:

type family Foo a b

data Goof a b where
  Goof :: !(Foo a b :~: Int) -> Goof a b

(:~:) has just one constructor (Refl) with no arguments, so I'd expect it to unpack to a void representation:

GoofConstr :: Foo a b ~N# Int => Goof a b
WGoof :: Foo a b :~: Int -> Goof a b
WGoof eq = case eq of Refl -> GoofConstr

But it doesn't seem to unpack at all.

Trac metadata

Trac field	Value
Version	8.2.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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