[GHC] #10503: The impossible happened (no skolem info) - untouchable kind variable
GHC
ghc-devs at haskell.org
Tue Jun 9 12:20:17 UTC 2015
#10503: The impossible happened (no skolem info) - untouchable kind variable
-------------------------------------+-------------------------------------
Reporter: | Owner:
AlekseyKliger | Status: new
Type: bug | Milestone:
Priority: normal | Version: 7.10.1
Component: Compiler | Operating System: Unknown/Multiple
Keywords: | Type of failure: Compile-time
Architecture: | crash
Unknown/Multiple | Blocked By:
Test Case: | Related Tickets:
Blocking: |
Differential Revisions: |
-------------------------------------+-------------------------------------
{{{#!hs
{-# LANGUAGE RankNTypes, PolyKinds, DataKinds, TypeFamilies #-}
module GHCBug where
data Proxy p = Proxy
data KProxy (a :: *) = KProxy
h :: forall r . (Proxy ('KProxy :: KProxy k) ~ Proxy ('KProxy :: KProxy *)
=> r) -> r
h = undefined
}}}
GHC reports
{{{
GHCBug.hs:8:6:
Couldn't match kind ‘k’ with ‘*’
‘k’ is untouchable
inside the constraints (Proxy 'KProxy ~ Proxy 'KProxy)
bound by the type signature for
h :: (Proxy 'KProxy ~ Proxy 'KProxy) => r
at GHCBug.hs:8:6-87ghc: panic! (the 'impossible' happened)
(GHC version 7.10.1 for x86_64-unknown-linux):
No skolem info: k_amc[sk]
}}}
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10503>
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