When a type application cannot be applied to an identifier due to the absence of an explicit type signature, let the error just say so!

Consider this code:

{-# language TypeApplications #-}

module TypeApplicationsErrorMessage where

f = (+)
g = f @Integer

This is what happens when I try to compile it:

% ghc TypeApplicationsErrorMessage.hs
[1 of 1] Compiling TypeApplicationsErrorMessage ( TypeApplicationsErrorMessage.hs, TypeApplicationsErrorMessage.o )

TypeApplicationsErrorMessage.hs:6:5: error:
    • Cannot apply expression of type ‘a0 -> a0 -> a0’
      to a visible type argument ‘Integer’
    • In the expression: f @Integer
      In an equation for ‘g’: g = f @Integer
  |
6 | g = f @Integer
  |     ^^^^^^^^^^

This error is easily fixed by supplying an explicit type signature to f. So, perhaps the error message could just say so?

I am observing this with The Glorious Glasgow Haskell Compilation System, version 8.6.0.20180810.

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