Error message points to wrong location

This rightly fails, but I have an issue with the error message. I think points to the visible type application eagerly.. rather than the type annotation (f_xx :: ()).

{-# Language RankNTypes, PolyKinds, GADTs, TypeApplications, ScopedTypeVariables #-}

import Data.Kind

newtype Limit :: (k -> Type) -> Type where
  Limit :: (forall xx. f xx) -> Limit f

foo :: forall f a. Limit f -> f a
foo (Limit (f_xx :: ())) = f_xx @a

gives

$ ghci -ignore-dot-ghci /tmp/Test.hs 
GHCi, version 8.5.20180105: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( /tmp/Test.hs, interpreted )

/tmp/Test.hs:9:28: error:
    • Cannot apply expression of type ‘()’
      to a visible type argument ‘a’
    • In the expression: f_xx @a
      In an equation for ‘foo’: foo (Limit (f_xx :: ())) = f_xx @a
  |
9 | foo (Limit (f_xx :: ())) = f_xx @a
  |                            ^^^^^^^
Failed, no modules loaded.
Prelude> 

I would have expected:

/tmp/Test.hs:9:13: error:
    • Couldn't match expected type ‘()’ with actual type ‘f xx0’
    • When checking that the pattern signature: ()
        fits the type of its context: forall (xx :: k1). f xx
      In the pattern: f_xx :: ()
      In the pattern: Limit (f_xx :: ())
    • Relevant bindings include
        foo :: Limit f -> f a (bound at /tmp/Test.hs:9:1)

Thoughts

Trac metadata

Trac field	Value
Version	8.5
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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