Regression: Detection of unused imports is imprecise (since GHC 8.0.1)
GHCs detection of unused imports used to be very precise. But apparently this changed with GHC 8.0.1. I already noticed for a while that there is something fishy going on and finally came up with a minimal example.
Steps to reproduce:
-- Bar.hs module Bar (bar, module Control.Monad) where import Control.Monad bar :: Integer bar = 23
-- Foo.hs module Foo where import Bar import Control.Monad (forM_) foo :: Monad m => [a] -> (a -> m ()) -> m () foo = forM_ baz :: Integer baz = bar
$ ghci -Wall -Werror Foo.hs
- *Expected result:** The program is reject.
- *Actual result:** The program was reject by GHC < 8.0.1, however later versions of GHC accept the program.