Hai Nguyen Quang authored May 24, 2023 and Marge Bot committed May 24, 2023

This patch migrates the error messages in GHC.Tc.Validity to use
the new diagnostic infrastructure.

It adds the constructors:

  - TcRnSimplifiableConstraint
  - TcRnArityMismatch
  - TcRnIllegalInstanceDecl, with sub-datatypes for HasField errors
    and fundep coverage condition errors.