unhelpful error message about enabling TypeApplications

% cat bug.hs

{-# LANGUAGE TypeApplications #-}
main = return (id@() ())

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

bug.hs:2:16: error:
    Pattern syntax in expression context: id@()
    Did you mean to enable TypeApplications?

This error message makes no sense because TypeApplications is already enabled.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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