panic in GHC 8.10.1: No skolem info
Summary
GHC 8.10.1 panics on this file:
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE TypeFamilies #-}
module Main where
import Data.Type.Equality (type (:~:)(Refl))
type family Op :: m -> m -> m
type family Unit :: m
class M (m :: k) where
idl :: forall (x :: m). (Op Unit x) :~: x
bug.hs:10:36: error:ghc: panic! (the 'impossible' happened)
(GHC version 8.10.1:
No skolem info:
[k_aiM[sk:1]]
Call stack:
CallStack (from HasCallStack):
callStackDoc, called at compiler/utils/Outputable.hs:1179:37 in ghc:Outputable
pprPanic, called at compiler/typecheck/TcErrors.hs:2943:5 in ghc:TcErrors
Please report this as a GHC bug: https://www.haskell.org/ghc/reportabug
Steps to reproduce
Just compile the above with GHC 8.10.1
Expected behavior
I'm not sure - the above declarations might be nonsensical and deserve an error message?
Environment
- GHC version used: 8.10.1
Optional:
- Operating System:
- System Architecture: