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This type-incorrect program gives a wrong error message:

main = tmp "hello"
  where tmp :: String -> IO ()
        tmp = sequence_ lst
        lst = [putStrLn "hi"]

Namely:

    Couldn't match expected type `IO ()' with actual type `()'
    Expected type: String -> IO ()
      Actual type: String -> ()
    In the return type of a call of `sequence_'
    In the expression: sequence_ lst

I would not expect the "actual type" to be "String -> ()", but rather "IO ()". Note: GHC expects that "(->) String" is a monad.

Trac metadata

Trac field	Value
Version	7.6.3
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
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