#2146: Decomposition rule for equalities is too weak in case of higher-kinded
type
families
-------------------------------------+--------------------------------------
Reporter: chak | Owner: chak
Type: bug | Status: new
Priority: normal | Milestone: 6.10 branch
Component: Compiler (Type checker) | Version: 6.9
Severity: minor | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Architecture: Multiple
Os: Multiple |
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Comment (by chak):
Another example from #2418:
{{{
{-# OPTIONS_GHC -fglasgow-exts #-}
class Blah f a where blah :: a -> T f f a
class A f where type T f :: (* -> *) -> * -> *
-- wrapper :: forall a f tf . (Blah f a,T f~tf) => a -> tf f a
wrapper :: forall a f . (Blah f a) => a -> T f f a
wrapper x = blah x
}}}
Add both examples to the test suite.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2146#comment:2>
GHC <http://www.haskell.org/ghc/>
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