Warning for unused existentially quantified types
I found a bug in my code that boils down to:
{-# LANGUAGE ExistentialQuantification #-}
data X = forall a b. X a
Obviously the type 'b' is not used. It didn't hurt, but it could have been, that I intended to do something with the 'b' and then forgot it. I would like to get a warning in this situation like "Unused type variable 'b'".
It might even be, that no existential quantification is needed at all, as in the following case:
data Y = forall a. Y
Trac metadata
Trac field | Value |
---|---|
Version | 6.12.3 |
Type | FeatureRequest |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
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Blocking | |
CC | ghc@henning-thielemann.de |
Operating system | |
Architecture |