Pattern match checking, bang patterns and newtypes

Here's another bugger:

{-# OPTIONS_GHC -Wincomplete-patterns -fforce-recomp #-}
{-# LANGUAGE BangPatterns #-}
module Lib where

newtype IInt = IInt Int

f :: IInt -> Bool -> ()
f !(IInt _) True = ()
f (IInt 42) True = ()
f _         _    = ()

warns

blub.hs:9:1: warning: [-Woverlapping-patterns]
    Pattern match has inaccessible right hand side
    In an equation for ‘f’: f (IInt 42) True = ...
  |
9 | f (IInt 42) True = ()
  | ^^^^^^^^^^^^^^^^^^^^^

Which is too imprecise: Actually the line is redundant. If you delete it, f (IInt $ error "boom") True will still crash.