Pmc: Consider long-distance information when warning about OverloadedRecordDot

Consider

{-# LANGUAGE GADTs, OverloadedRecordDot #-}

module Lib where

data T a where
  T1 :: T Int
  T2 :: {sel :: Int} -> T Bool
  T3 :: T Bool

f :: T Bool -> Int
f x = x.sel -- warn

data Dot = No | Yes {sel2 :: Int}

ldiDot :: Dot -> Int
ldiDot No = 0
ldiDot d  = d.sel2 -- do not warn

We should warn about f, but not about ldiDot, because in the latter case we will never select on No because of the ambient pattern-match.

Currently, we warn about both occurrences, a shortcoming of the current approach to -Wincomplete-record-selectors.