#7347: Existential data constructors should not be promoted
---------------------------------+------------------------------------------
Reporter: simonpj | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.6.1
Keywords: | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: None/Unknown
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Comment(by kosmikus):
I'm sorry. I was confused by the fact that if I load a file containing
{{{
data Ex = forall a. MkEx a
}}}
into GHCi, I get this:
{{{
*Main> :kind 'MkEx
'MkEx :: * -> Ex
}}}
But I note now that this is because I didn't say `PolyKinds` in GHCi.
Indeed, then I get:
{{{
*Main> :set -XPolyKinds
*Main> :kind 'MkEx
'MkEx :: k -> Ex
}}}
So I thought GHC would not promote to an existential quantification on the
type level, but it actually does. So yes, I was wrong, and this is indeed
problematic.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7347#comment:7>
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