Failed Instance Resolution for State

[pseudonom]

If I define

module Foo where

import qualified Control.Monad.State as ST
import qualified Control.Monad.State.Class as ST

ident :: forall a. a -> a
ident a = a
ident' :: Number -> Number
ident' a = a

then

a :: ST.State Number Unit
a = ST.modify ident'

compiles/works fine.

However,

a :: ST.State Number Unit
a = ST.modify ident

complains that

No instance found for Control.Monad.State.Class.MonadState u7 (Control.Monad.State.Trans.StateT Prim.Number Data.Identity.Identity)

.

(Both versions work in Haskell.)

[hdgarrood]

I think the solution to this might be functional dependencies, which would make this a duplicate of purescript/purescript#1580. Not entirely sure, though.

[garyb]

I'm pretty sure this is related to the lack of functional dependencies too, so this should be fixed in the next release.