Wrong error message for unknown Instance
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) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |