#4494: Another regression with type families
----------------------------------------+-----------------------------------
Reporter: rl | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler (Type checker) | Version: 7.1
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: GHC rejects valid
program
----------------------------------------+-----------------------------------
Comment(by rl):
This:
{{{
{-# LANGUAGE TypeFamilies, RankNTypes, FlexibleContexts,
ScopedTypeVariables #-}
module T4494 where
type family H s a b
class D (G v) => C v where
type G v
type F v
foo :: v -> H (F v) (G v) v
class D s where
bar :: (forall t. Maybe t -> a) -> s -> H a s r -> r
call :: forall v. C v => F v -> v
call x = bar' (\_ -> x)
(undefined :: G v)
(foo (undefined :: v))
bar' :: C v => (forall t. Maybe t -> F v) -> G v -> H (F v) (G v) v -> v
bar' = bar
}}}
Why did you use !NoScopedTypeVariables instead of !ScopedTypeVariables?
Must be Friday evening!
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4494#comment:5>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
_______________________________________________
Glasgow-haskell-bugs mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
