regression in -Wunused-pattern-binds
{-# LANGUAGE TemplateHaskell #-}
module TTT where
a :: ()
a = let () = () in ()
b :: ()
b = let $([p|()|]) = () in ()
on ghc-9.2.2 this produces the warnings:
[nix-shell:~/ghc-clean]$ ghc TTT.hs -Wall -fforce-recomp
[1 of 1] Compiling TTT ( TTT.hs, TTT.o, TTT.dyn_o )
TTT.hs:5:9: warning: [-Wunused-pattern-binds]
This pattern-binding binds no variables: () = ()
|
5 | a = let () = () in ()
| ^^^^^^^
TTT.hs:8:9: warning: [-Wunused-pattern-binds]
This pattern-binding binds no variables: (()) = ()
|
8 | b = let $([p|()|]) = () in ()
| ^^^^^^^^^^^^^^^
But on HEAD we only get the first warning. I have a fix.