diff options
Diffstat (limited to 'compiler/GHC/Tc/Instance/Class.hs')
| -rw-r--r-- | compiler/GHC/Tc/Instance/Class.hs | 33 |
1 files changed, 23 insertions, 10 deletions
diff --git a/compiler/GHC/Tc/Instance/Class.hs b/compiler/GHC/Tc/Instance/Class.hs index df7046c4fd..50a13ba901 100644 --- a/compiler/GHC/Tc/Instance/Class.hs +++ b/compiler/GHC/Tc/Instance/Class.hs @@ -33,6 +33,7 @@ import GHC.Types.SafeHaskell import GHC.Types.Name ( Name, pprDefinedAt ) import GHC.Types.Var.Env ( VarEnv ) import GHC.Types.Id +import GHC.Types.Var import GHC.Core.Predicate import GHC.Core.InstEnv @@ -96,13 +97,22 @@ data ClsInstResult | NotSure -- Multiple matches and/or one or more unifiers -data InstanceWhat - = BuiltinInstance - | BuiltinEqInstance -- A built-in "equality instance"; see the - -- GHC.Tc.Solver.InertSet Note [Solved dictionaries] - | LocalInstance - | TopLevInstance { iw_dfun_id :: DFunId - , iw_safe_over :: SafeOverlapping } +data InstanceWhat -- How did we solve this constraint? + = BuiltinEqInstance -- Built-in solver for (t1 ~ t2), (t1 ~~ t2), Coercible t1 t2 + -- See GHC.Tc.Solver.InertSet Note [Solved dictionaries] + + | BuiltinTypeableInstance TyCon -- Built-in solver for Typeable (T t1 .. tn) + -- See Note [Well-staged instance evidence] + + | BuiltinInstance -- Built-in solver for (C t1 .. tn) where C is + -- KnownNat, .. etc (classes with no top-level evidence) + + | LocalInstance -- Solved by a quantified constraint + -- See GHC.Tc.Solver.InertSet Note [Solved dictionaries] + + | TopLevInstance -- Solved by a top-level instance decl + { iw_dfun_id :: DFunId + , iw_safe_over :: SafeOverlapping } instance Outputable ClsInstResult where ppr NoInstance = text "NoInstance" @@ -113,6 +123,7 @@ instance Outputable ClsInstResult where instance Outputable InstanceWhat where ppr BuiltinInstance = text "a built-in instance" + ppr BuiltinTypeableInstance {} = text "a built-in typeable instance" ppr BuiltinEqInstance = text "a built-in equality instance" ppr LocalInstance = text "a locally-quantified instance" ppr (TopLevInstance { iw_dfun_id = dfun }) @@ -127,6 +138,7 @@ instanceReturnsDictCon :: InstanceWhat -> Bool -- See Note [Solved dictionaries] in GHC.Tc.Solver.InertSet instanceReturnsDictCon (TopLevInstance {}) = True instanceReturnsDictCon BuiltinInstance = True +instanceReturnsDictCon BuiltinTypeableInstance {} = True instanceReturnsDictCon BuiltinEqInstance = False instanceReturnsDictCon LocalInstance = False @@ -462,9 +474,10 @@ doFunTy clas ty mult arg_ty ret_ty doTyConApp :: Class -> Type -> TyCon -> [Kind] -> TcM ClsInstResult doTyConApp clas ty tc kind_args | tyConIsTypeable tc - = return $ OneInst { cir_new_theta = (map (mk_typeable_pred clas) kind_args) - , cir_mk_ev = mk_ev - , cir_what = BuiltinInstance } + = do + return $ OneInst { cir_new_theta = (map (mk_typeable_pred clas) kind_args) + , cir_mk_ev = mk_ev + , cir_what = BuiltinTypeableInstance tc } | otherwise = return NoInstance where |