User guide section on AllowAmbiguousTypes should mention TypeApplications

https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts.html?highlight=allowambiguoustypes#ghc-flag--XAllowAmbiguousTypes

With type applications it is tempting to write

class C x a where
    meth :: a

which will fail the ambiguity check as x is not used in any methods. One way to get around this is to use TypeApplications in order to specify what x should be at each usage of meth. A small section in the user guide explaining this and linking to the section on TypeApplications would be useful.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture