#15419: GHC 8.6.1 regression (buildKindCoercion) -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: goldfire Type: bug | Status: new Priority: highest | Milestone: 8.6.1 Component: Compiler (Type | Version: 8.5 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: #15346 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * related: => #15346 Comment: Amusingly enough, I think this simply a symptom of #15346. I tried applying this patch: {{{#!diff diff --git a/compiler/coreSyn/CoreOpt.hs b/compiler/coreSyn/CoreOpt.hs index 8684c84..11cbd1e 100644 --- a/compiler/coreSyn/CoreOpt.hs +++ b/compiler/coreSyn/CoreOpt.hs @@ -979,7 +979,7 @@ pushCoTyArg co ty | isForAllTy tyL = ASSERT2( isForAllTy tyR, ppr co $$ ppr ty ) - Just (ty `mkCastTy` mkSymCo co1, MCo co2) + Just (ty `mkCastTy` co1, MCo co2) | otherwise = Nothing @@ -989,8 +989,8 @@ pushCoTyArg co ty -- tyL = forall (a1 :: k1). ty1 -- tyR = forall (a2 :: k2). ty2 - co1 = mkNthCo Nominal 0 co - -- co1 :: k1 ~N k2 + co1 = mkSymCo (mkNthCo Nominal 0 co) + -- co1 :: k2 ~N k1 -- Note that NthCo can extract a Nominal equality between the -- kinds of the types related by a coercion between forall-types. -- See the NthCo case in CoreLint. diff --git a/compiler/types/Coercion.hs b/compiler/types/Coercion.hs index 2ca5151..1557ce0 100644 --- a/compiler/types/Coercion.hs +++ b/compiler/types/Coercion.hs @@ -1812,7 +1812,7 @@ liftCoSubstVarBndrUsing fun lc@(LC subst cenv) old_var Pair k1 _ = coercionKind eta new_var = uniqAway (getTCvInScope subst) (setVarType old_var k1) - lifted = Refl (TyVarTy new_var) + lifted = GRefl Nominal (TyVarTy new_var) (MCo eta) new_cenv = extendVarEnv cenv old_var lifted -- | Is a var in the domain of a lifting context? }}} And with that, the program in this ticket no longer panics. Richard, you're currently validating this patch, yes? Would you mind adding this as a regression test? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15419#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler