Rebindable syntax creates bogus warning

{-# LANGUAGE RebindableSyntax #-}


import Data.Void
import Prelude ((.), ($), Int, id, Num(..))


(>>) :: (b -> c) -> (a -> b) -> (a -> c)
(>>) = (.)


return :: Void -> Void
return = absurd


run :: a -> (a -> b) -> b
run x f = f x


result :: Int
result = run 8 $ do
    \n -> n * n
    id
    (+ 7)
    (* 2)

Compile with -Wall issues incorrect warnings. In fact the suggested fixes cause compile errors if implemented.

Test.hs:22:5: Warning:
    A do-notation statement discarded a result of type Int.
    Suppress this warning by saying "_ <- \ n -> (*) n n",
    or by using the flag -fno-warn-unused-do-bind

Test.hs:23:5: Warning:
    A do-notation statement discarded a result of type Int.
    Suppress this warning by saying "_ <- id",
    or by using the flag -fno-warn-unused-do-bind

Test.hs:24:5: Warning:
    A do-notation statement discarded a result of type Int.
    Suppress this warning by saying "_ <- (( \ x_ -> (+) x_ 7))",
    or by using the flag -fno-warn-unused-do-bind

Trac metadata

Trac field	Value
Version	7.6.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Windows
Architecture