missing "incomplete-patterns" warning for TH-generated functions

"incomplete-patterns" warnings are generated for TH-generated case expressions, but not for TH-generated functions, so the behaviour is inconsistent.

For example:

{-# LANGUAGE TemplateHaskell #-}
module Lib where
import Language.Haskell.TH

qIncompleteCase :: Q [Dec]
qIncompleteCase = [d|
  incompleteCase :: Bool -> ()
  incompleteCase b = case b of
    True -> () |]

qIncompleteFunction :: Q [Dec]
qIncompleteFunction =[d|
  incompleteFunction :: Bool -> ()
  incompleteFunction True = () |]

{-# LANGUAGE TemplateHaskell #-}
module Bug where
import Lib

$qIncompleteCase

$qIncompleteFunction

incompleteCase' :: Bool -> ()
incompleteCase' b = case b of
  True -> ()

incompleteFunction' :: Bool -> ()
incompleteFunction' True = ()

When compiling the above two files with -Wall, GHC 8.2.2 produces an "incomplete-patterns" warning for qIncompleteCase, incompleteCase', and incompleteFunction', but not for qIncompleteFunction. I would prefer to get a warning for qIncompleteFunction as well.

My use case is the surjective package, in which I intentionally generate code which produces warnings in order to warn the user about corresponding issues in their code. I could generate better error messages if GHC generated warnings for TH-generated functions as well.

Trac metadata

Trac field	Value
Version	8.2.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Template Haskell
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