Deprecate -XExplicitForAll

The problem is that it uses the same syntax as -XScopedTypeVariables to mean something a bit different, and incompatible. -XExplicitForAll is of rather limited utility, whereas -XScopedTypeVariables is a wonderful thing. Confusion is bad.

f :: forall a . a -> [a]
f a = let g :: a -> a
          g x = x
      in g [a]

Trac metadata

Trac field	Value
Version	7.8.3
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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