diff options
Diffstat (limited to 'compiler/GHC/Core/FamInstEnv.hs')
| -rw-r--r-- | compiler/GHC/Core/FamInstEnv.hs | 23 |
1 files changed, 12 insertions, 11 deletions
diff --git a/compiler/GHC/Core/FamInstEnv.hs b/compiler/GHC/Core/FamInstEnv.hs index 31d01d3893..121c8ffe10 100644 --- a/compiler/GHC/Core/FamInstEnv.hs +++ b/compiler/GHC/Core/FamInstEnv.hs @@ -24,7 +24,7 @@ module GHC.Core.FamInstEnv ( FamInstMatch(..), lookupFamInstEnv, lookupFamInstEnvConflicts, lookupFamInstEnvByTyCon, - isDominatedBy, apartnessCheck, + isDominatedBy, apartnessCheck, compatibleBranches, -- Injectivity InjectivityCheckResult(..), @@ -534,15 +534,16 @@ fails anyway. compatibleBranches :: CoAxBranch -> CoAxBranch -> Bool compatibleBranches (CoAxBranch { cab_lhs = lhs1, cab_rhs = rhs1 }) (CoAxBranch { cab_lhs = lhs2, cab_rhs = rhs2 }) - = let (commonlhs1, commonlhs2) = zipAndUnzip lhs1 lhs2 - -- See Note [Compatibility of eta-reduced axioms] - in case tcUnifyTysFG alwaysBindFun commonlhs1 commonlhs2 of - SurelyApart -> True - Unifiable subst - | Type.substTyAddInScope subst rhs1 `eqType` - Type.substTyAddInScope subst rhs2 - -> True - _ -> False + = case tcUnifyTysFG alwaysBindFun commonlhs1 commonlhs2 of + -- Here we need the cab_tvs of the two branches to be disinct. + -- See Note [CoAxBranch type variables] in GHC.Core.Coercion.Axiom. + SurelyApart -> True + MaybeApart {} -> False + Unifiable subst -> Type.substTyAddInScope subst rhs1 `eqType` + Type.substTyAddInScope subst rhs2 + where + (commonlhs1, commonlhs2) = zipAndUnzip lhs1 lhs2 + -- See Note [Compatibility of eta-reduced axioms] -- | Result of testing two type family equations for injectiviy. data InjectivityCheckResult @@ -597,7 +598,7 @@ computeAxiomIncomps branches where go :: [CoAxBranch] -> CoAxBranch -> ([CoAxBranch], CoAxBranch) go prev_brs cur_br - = (cur_br : prev_brs, new_br) + = (new_br : prev_brs, new_br) where new_br = cur_br { cab_incomps = mk_incomps prev_brs cur_br } |