haskell Type.hs ERROR

[ruoshuiwyl]

Env : opensuse 42.1 ghc 7.10.3
runhaskell step2,...,stepA
Types.hs:64:1:
Non type-variable argument
in the constraint: Control.Monad.Error.Class.MonadError MalError m
(Use FlexibleContexts to permit this)
When checking that ‘throwStr’ has the inferred type
throwStr :: forall (m :: * -> *) a.
Control.Monad.Error.Class.MonadError MalError m =>
String -> m a

Types.hs:65:1:
Non type-variable argument
in the constraint: Control.Monad.Error.Class.MonadError MalError m
(Use FlexibleContexts to permit this)
When checking that ‘throwMalVal’ has the inferred type
throwMalVal :: forall (m :: * -> *) a.
Control.Monad.Error.Class.MonadError MalError m =>
MalVal -> m a

[kanaka]

This is due to changes in ghc-7.10.1: http://stackoverflow.com/questions/28287329/ghc-7-10-non-type-variable-argument-use-flexiblecontexts-to-permit-this

You can get things to compile by adding -XFlexibleContexts to the ghc call in the makefile, however, there were also some refactorings to Error/Exception handling in 7.10.1 so you get lots of build warnings.

I think the correct fix for this issue is to refactor and clean up the error/except handling code in the mal implementation so that things compile cleanly without the compiler options. Ideally, 7.6 should also be supported since that's still seems pretty typical version in the wild.

Anybody with Haskell chops want to tackle this? I probably won't have a chance anytime soon.

[ruoshuiwyl]

Thank you.
I try to compile by addding -XFlexibleContexts.
It works.

[kanaka]

@ruoshuiwyl I would be interesting in hearing if you are able to use the latest changes from @prt2121 without requiring the -XFlexibleContexts hack

[ruoshuiwyl]

thank you. I try to it.