Issue2349-instance-hidden.agda:8,6-33
Instance arguments whose type does not end in a named or variable
type are never considered by instance search, so having an instance
argument ⦃ A : Set a ⦄ has no effect.
Issue2349-instance-hidden.agda:12,16-20
x != c {_} ⦃ _ ⦄ {a} of type D {ℓ} ⦃ A ⦄
when checking that the expression refl has type
_≡_ {ℓ} {D {ℓ} ⦃ A ⦄} x (c {_} ⦃ _ ⦄ {a})
