#7485: Tuple constraints not properly kinded
-----------------------------+----------------------------------------------
Reporter: goldfire | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.7 | Keywords: ConstraintKinds
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: None/Unknown | Blockedby:
Blocking: | Related:
-----------------------------+----------------------------------------------
Consider this:
{{{
{-# LANGUAGE DataKinds, ConstraintKinds, KindSignatures #-}
import GHC.Exts ( Constraint )
type UnitType = (() :: *)
type UnitConstraint = (() :: Constraint)
type PairType = ((,) :: * -> * -> *)
}}}
So far, so good. But, adding the following causes an error:
{{{
type PairConstraint = ((,) :: Constraint -> Constraint -> Constraint)
}}}
The error is
{{{
The signature specified kind `Constraint
-> Constraint -> Constraint',
but `(,)' has kind `* -> * -> *'
}}}
In general, you can't use the prefix form of {{{(,)}}} in a constraint, to
my surprise. It's not entirely clear what is the "correct" behavior here,
but this all seems a little fishy as currently implemented.
This was all tested on 7.7.20121130.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7485>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
_______________________________________________
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
