Phantom types confuse SpecConstr

This program

type T a = Int

f :: T a -> Bool -> [Int]
f x b = case b of
               True  -> f x b
               False -> x : f x (x > 19)

gave a Lint error in SpecConstr (use -O2). Reason: the specialised function was abstracted over x, but x's type mentions a phantom type variable a, and that ''wasn't'' being abstracted over.

Phantom type variables are a nuisance. A simple fix is to de-synonym the type of the abstracted variables.

Trac metadata

Trac field	Value
Version	7.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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