--------------------------------
-- Types
TcType, TcSigmaType, TcRhoType, TcTauType, TcPredType, TcThetaType,
- TcTyVar, TcTyVarSet, TcKind, TcCoVar,
+ TcCoercion, TcTyVar, TcTyVarSet, TcKind, TcCoVar,
--------------------------------
-- MetaDetails
UserTypeCtxt(..), pprUserTypeCtxt,
- TcTyVarDetails(..), pprTcTyVarDetails,
+ TcTyVarDetails(..), pprTcTyVarDetails, vanillaSkolemTv, superSkolemTv,
MetaDetails(Flexi, Indirect), MetaInfo(..),
- SkolemInfo(..), pprSkolTvBinding, pprSkolInfo,
isImmutableTyVar, isSkolemTyVar, isMetaTyVar, isMetaTyVarTy,
- isSigTyVar, isExistentialTyVar, isTyConableTyVar,
+ isSigTyVar, isOverlappableTyVar, isTyConableTyVar,
metaTvRef,
- isFlexi, isIndirect, isRuntimeUnk, isUnk,
+ isFlexi, isIndirect, isRuntimeUnkSkol,
--------------------------------
-- Builders
---------------------------------
-- Predicates.
-- Again, newtypes are opaque
- tcEqType, tcEqTypes, tcEqPred, tcCmpType, tcCmpTypes, tcCmpPred, tcEqTypeX,
+ eqType, eqTypes, eqPred, cmpType, cmpTypes, cmpPred, eqTypeX,
eqKind,
- isSigmaTy, isOverloadedTy, isRigidTy,
+ isSigmaTy, isOverloadedTy,
isDoubleTy, isFloatTy, isIntTy, isWordTy, isStringTy,
isIntegerTy, isBoolTy, isUnitTy, isCharTy,
isTauTy, isTauTyCon, tcIsTyVarTy, tcIsForAllTy,
---------------------------------
-- Misc type manipulators
deNoteType,
- tyClsNamesOfType, tyClsNamesOfDFunHead,
+ orphNamesOfType, orphNamesOfDFunHead, orphNamesOfCo,
getDFunTyKey,
---------------------------------
-- Predicate types
- getClassPredTys_maybe, getClassPredTys,
- isClassPred, isTyVarClassPred, isEqPred,
- mkClassPred, mkIPPred, tcSplitPredTy_maybe,
- mkDictTy, evVarPred,
- isPredTy, isDictTy, isDictLikeTy,
- tcSplitDFunTy, tcSplitDFunHead, predTyUnique,
- isIPPred,
- isRefineableTy, isRefineablePred,
+ mkMinimalBySCs, transSuperClasses, immSuperClasses,
-- * Tidying type related things up for printing
tidyType, tidyTypes,
tidyTyVarBndr, tidyFreeTyVars,
tidyOpenTyVar, tidyOpenTyVars,
tidyTopType, tidyPred,
- tidyKind, tidySkolemTyVar,
+ tidyKind,
+ tidyCo, tidyCos,
---------------------------------
-- Foreign import and export
tcSplitIOType_maybe, -- :: Type -> Maybe Type
--------------------------------
- -- Rexported from Coercion
- typeKind,
-
- --------------------------------
- -- Rexported from Type
- Kind, -- Stuff to do with kinds is insensitive to pre/post Tc
+ -- Rexported from Kind
+ Kind, typeKind,
unliftedTypeKind, liftedTypeKind, argTypeKind,
openTypeKind, mkArrowKind, mkArrowKinds,
isLiftedTypeKind, isUnliftedTypeKind, isSubOpenTypeKind,
isSubArgTypeKind, isSubKind, splitKindFunTys, defaultKind,
kindVarRef, mkKindVar,
- Type, PredType(..), ThetaType,
+ --------------------------------
+ -- Rexported from Type
+ Type, Pred(..), PredType, ThetaType,
mkForAllTy, mkForAllTys,
mkFunTy, mkFunTys, zipFunTys,
mkTyConApp, mkAppTy, mkAppTys, applyTy, applyTys,
mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
+ getClassPredTys_maybe, getClassPredTys,
+ isClassPred, isTyVarClassPred, isEqPred,
+ mkClassPred, mkIPPred, splitPredTy_maybe,
+ mkDictTy, isPredTy, isDictTy, isDictLikeTy,
+ tcSplitDFunTy, tcSplitDFunHead,
+ isIPPred, mkEqPred,
+
-- Type substitutions
TvSubst(..), -- Representation visible to a few friends
- TvSubstEnv, emptyTvSubst, substEqSpec,
+ TvSubstEnv, emptyTvSubst,
mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst,
mkTopTvSubst, notElemTvSubst, unionTvSubst,
- getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, lookupTyVar,
- extendTvSubst, extendTvSubstList, isInScope, mkTvSubst, zipTyEnv,
- substTy, substTys, substTyWith, substTheta, substTyVar, substTyVars, substTyVarBndr,
+ getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope,
+ Type.lookupTyVar, Type.extendTvSubst, Type.substTyVarBndr,
+ extendTvSubstList, isInScope, mkTvSubst, zipTyEnv,
+ Type.substTy, substTys, substTyWith, substTheta, substTyVar, substTyVars,
isUnLiftedType, -- Source types are always lifted
isUnboxedTupleType, -- Ditto
pprKind, pprParendKind,
pprType, pprParendType, pprTypeApp, pprTyThingCategory,
- pprPred, pprTheta, pprThetaArrow, pprClassPred
+ pprPred, pprTheta, pprThetaArrow, pprThetaArrowTy, pprClassPred
) where
#include "HsVersions.h"
-- friends:
+import Kind
import TypeRep
-import DataCon
import Class
import Var
import ForeignCall
import Type
import Coercion
import TyCon
-import HsExpr( HsMatchContext )
-- others:
import DynFlags
-import Name
+import Name hiding (varName)
import NameSet
import VarEnv
import PrelNames
-- a cannot occur inside a MutTyVar in T; that is,
-- T is "flattened" before quantifying over a
+type TcCoercion = Coercion -- A TcCoercion can contain TcTypes.
+
-- These types do not have boxy type variables in them
type TcPredType = PredType
type TcThetaType = ThetaType
The alternative (currently implemented) is to have a special kind of skolem
constant, SigTv, which can unify with other SigTvs. These are *not* treated
-as righd for the purposes of GADTs. And they are used *only* for pattern
+as rigid for the purposes of GADTs. And they are used *only* for pattern
bindings and mutually recursive function bindings. See the function
TcBinds.tcInstSig, and its use_skols parameter.
\begin{code}
-- A TyVarDetails is inside a TyVar
data TcTyVarDetails
- = SkolemTv SkolemInfo -- A skolem constant
+ = SkolemTv -- A skolem
+ Bool -- True <=> this skolem type variable can be overlapped
+ -- when looking up instances
+ -- See Note [Binding when looking up instances] in InstEnv
+
+ | RuntimeUnk -- Stands for an as-yet-unknown type in the GHCi
+ -- interactive context
- | FlatSkol TcType
+ | FlatSkol TcType
-- The "skolem" obtained by flattening during
-- constraint simplification
| MetaTv MetaInfo (IORef MetaDetails)
+vanillaSkolemTv, superSkolemTv :: TcTyVarDetails
+-- See Note [Binding when looking up instances] in InstEnv
+vanillaSkolemTv = SkolemTv False -- Might be instantiated
+superSkolemTv = SkolemTv True -- Treat this as a completely distinct type
+
data MetaDetails
= Flexi -- Flexi type variables unify to become Indirects
| Indirect TcType
-data MetaInfo
+instance Outputable MetaDetails where
+ ppr Flexi = ptext (sLit "Flexi")
+ ppr (Indirect ty) = ptext (sLit "Indirect") <+> ppr ty
+
+data MetaInfo
= TauTv -- This MetaTv is an ordinary unification variable
-- A TauTv is always filled in with a tau-type, which
-- never contains any ForAlls
- | SigTv Name -- A variant of TauTv, except that it should not be
+ | SigTv -- A variant of TauTv, except that it should not be
-- unified with a type, only with a type variable
-- SigTvs are only distinguished to improve error messages
-- see Note [Signature skolems]
-- The MetaDetails, if filled in, will
-- always be another SigTv or a SkolemTv
- -- The Name is the name of the function from whose
- -- type signature we got this skolem
| TcsTv -- A MetaTv allocated by the constraint solver
-- Its particular property is that it is always "touchable"
-- Nevertheless, the constraint solver has to try to guess
-- what type to instantiate it to
-----------------------------------
--- SkolemInfo describes a site where
--- a) type variables are skolemised
--- b) an implication constraint is generated
-data SkolemInfo
- = SigSkol UserTypeCtxt -- A skolem that is created by instantiating
- -- a programmer-supplied type signature
- -- Location of the binding site is on the TyVar
-
- -- The rest are for non-scoped skolems
- | ClsSkol Class -- Bound at a class decl
- | InstSkol -- Bound at an instance decl
- | FamInstSkol -- Bound at a family instance decl
- | PatSkol -- An existential type variable bound by a pattern for
- DataCon -- a data constructor with an existential type.
- (HsMatchContext Name)
- -- e.g. data T = forall a. Eq a => MkT a
- -- f (MkT x) = ...
- -- The pattern MkT x will allocate an existential type
- -- variable for 'a'.
-
- | ArrowSkol -- An arrow form (see TcArrows)
-
- | IPSkol [IPName Name] -- Binding site of an implicit parameter
-
- | RuleSkol RuleName -- The LHS of a RULE
- | GenSkol TcType -- Bound when doing a subsumption check for ty
- | RuntimeUnkSkol -- a type variable used to represent an unknown
- -- runtime type (used in the GHCi debugger)
-
- | NoScSkol -- Used for the "self" superclass when solving
- -- superclasses; don't generate superclasses of me
-
- | UnkSkol -- Unhelpful info (until I improve it)
-
-------------------------------------
--- UserTypeCtxt describes the places where a
--- programmer-written type signature can occur
--- Like SkolemInfo, no location info
-data UserTypeCtxt
+-- UserTypeCtxt describes the origin of the polymorphic type
+-- in the places where we need to an expression has that type
+
+data UserTypeCtxt
= FunSigCtxt Name -- Function type signature
-- Also used for types in SPECIALISE pragmas
| ExprSigCtxt -- Expression type signature
| SpecInstCtxt -- SPECIALISE instance pragma
| ThBrackCtxt -- Template Haskell type brackets [t| ... |]
+ | GenSigCtxt -- Higher-rank or impredicative situations
+ -- e.g. (f e) where f has a higher-rank type
+ -- We might want to elaborate this
+
-- Notes re TySynCtxt
-- We allow type synonyms that aren't types; e.g. type List = []
--
\begin{code}
pprTcTyVarDetails :: TcTyVarDetails -> SDoc
-- For debugging
-pprTcTyVarDetails (SkolemTv _) = ptext (sLit "sk")
-pprTcTyVarDetails (FlatSkol {}) = ptext (sLit "fsk")
-pprTcTyVarDetails (MetaTv TauTv _) = ptext (sLit "tau")
-pprTcTyVarDetails (MetaTv TcsTv _) = ptext (sLit "tcs")
-pprTcTyVarDetails (MetaTv (SigTv _) _) = ptext (sLit "sig")
+pprTcTyVarDetails (SkolemTv {}) = ptext (sLit "sk")
+pprTcTyVarDetails (RuntimeUnk {}) = ptext (sLit "rt")
+pprTcTyVarDetails (FlatSkol {}) = ptext (sLit "fsk")
+pprTcTyVarDetails (MetaTv TauTv _) = ptext (sLit "tau")
+pprTcTyVarDetails (MetaTv TcsTv _) = ptext (sLit "tcs")
+pprTcTyVarDetails (MetaTv SigTv _) = ptext (sLit "sig")
pprUserTypeCtxt :: UserTypeCtxt -> SDoc
pprUserTypeCtxt (FunSigCtxt n) = ptext (sLit "the type signature for") <+> quotes (ppr n)
pprUserTypeCtxt (ForSigCtxt n) = ptext (sLit "the foreign declaration for") <+> quotes (ppr n)
pprUserTypeCtxt DefaultDeclCtxt = ptext (sLit "a type in a `default' declaration")
pprUserTypeCtxt SpecInstCtxt = ptext (sLit "a SPECIALISE instance pragma")
-
-pprSkolTvBinding :: TcTyVar -> SDoc
--- Print info about the binding of a skolem tyvar,
--- or nothing if we don't have anything useful to say
-pprSkolTvBinding tv
- = ASSERT ( isTcTyVar tv )
- quotes (ppr tv) <+> ppr_details (tcTyVarDetails tv)
- where
- ppr_details (SkolemTv info) = ppr_skol info
- ppr_details (FlatSkol {}) = ptext (sLit "is a flattening type variable")
- ppr_details (MetaTv (SigTv n) _) = ptext (sLit "is bound by the type signature for")
- <+> quotes (ppr n)
- ppr_details (MetaTv _ _) = ptext (sLit "is a meta type variable")
-
- ppr_skol UnkSkol = ptext (sLit "is an unknown type variable") -- Unhelpful
- ppr_skol RuntimeUnkSkol = ptext (sLit "is an unknown runtime type")
- ppr_skol info = sep [ptext (sLit "is a rigid type variable bound by"),
- sep [pprSkolInfo info,
- nest 2 (ptext (sLit "at") <+> ppr (getSrcLoc tv))]]
-
-pprSkolInfo :: SkolemInfo -> SDoc
--- Complete the sentence "is a rigid type variable bound by..."
-pprSkolInfo (SigSkol ctxt) = pprUserTypeCtxt ctxt
-pprSkolInfo (IPSkol ips) = ptext (sLit "the implicit-parameter bindings for")
- <+> pprWithCommas ppr ips
-pprSkolInfo (ClsSkol cls) = ptext (sLit "the class declaration for") <+> quotes (ppr cls)
-pprSkolInfo InstSkol = ptext (sLit "the instance declaration")
-pprSkolInfo NoScSkol = ptext (sLit "the instance declaration (self)")
-pprSkolInfo FamInstSkol = ptext (sLit "the family instance declaration")
-pprSkolInfo (RuleSkol name) = ptext (sLit "the RULE") <+> doubleQuotes (ftext name)
-pprSkolInfo ArrowSkol = ptext (sLit "the arrow form")
-pprSkolInfo (PatSkol dc _) = sep [ ptext (sLit "a pattern with constructor")
- , ppr dc <+> dcolon <+> ppr (dataConUserType dc) ]
-pprSkolInfo (GenSkol ty) = sep [ ptext (sLit "the polymorphic type")
- , quotes (ppr ty) ]
-
--- UnkSkol
--- For type variables the others are dealt with by pprSkolTvBinding.
--- For Insts, these cases should not happen
-pprSkolInfo UnkSkol = WARN( True, text "pprSkolInfo: UnkSkol" ) ptext (sLit "UnkSkol")
-pprSkolInfo RuntimeUnkSkol = WARN( True, text "pprSkolInfo: RuntimeUnkSkol" ) ptext (sLit "RuntimeUnkSkol")
-
-instance Outputable MetaDetails where
- ppr Flexi = ptext (sLit "Flexi")
- ppr (Indirect ty) = ptext (sLit "Indirect") <+> ppr ty
+pprUserTypeCtxt GenSigCtxt = ptext (sLit "a type expected by the context")
\end{code}
--
-- It doesn't change the uniques at all, just the print names.
tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
-tidyTyVarBndr env@(tidy_env, subst) tyvar
- = case tidyOccName tidy_env (getOccName name) of
- (tidy', occ') -> ((tidy', subst'), tyvar'')
+tidyTyVarBndr (tidy_env, subst) tyvar
+ = case tidyOccName tidy_env occ1 of
+ (tidy', occ') -> ((tidy', subst'), tyvar')
where
- subst' = extendVarEnv subst tyvar tyvar''
- tyvar' = setTyVarName tyvar name'
- name' = tidyNameOcc name occ'
- -- Don't forget to tidy the kind for coercions!
- tyvar'' | isCoVar tyvar = setTyVarKind tyvar' kind'
- | otherwise = tyvar'
- kind' = tidyType env (tyVarKind tyvar)
+ subst' = extendVarEnv subst tyvar tyvar'
+ tyvar' = setTyVarName tyvar name'
+ name' = tidyNameOcc name occ'
where
name = tyVarName tyvar
+ occ = getOccName name
+ -- System Names are for unification variables;
+ -- when we tidy them we give them a trailing "0" (or 1 etc)
+ -- so that they don't take precedence for the un-modified name
+ occ1 | isSystemName name = mkTyVarOcc (occNameString occ ++ "0")
+ | otherwise = occ
+
---------------
tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv
tidyTopType ty = tidyType emptyTidyEnv ty
---------------
-tidySkolemTyVar :: TidyEnv -> TcTyVar -> (TidyEnv, TcTyVar)
--- Tidy the type inside a GenSkol, preparatory to printing it
-tidySkolemTyVar env tv
- = ASSERT( isTcTyVar tv && (isSkolemTyVar tv || isSigTyVar tv ) )
- (env1, mkTcTyVar (tyVarName tv) (tyVarKind tv) info1)
- where
- (env1, info1) = case tcTyVarDetails tv of
- SkolemTv info -> (env1, SkolemTv info')
- where
- (env1, info') = tidy_skol_info env info
- info -> (env, info)
-
- tidy_skol_info env (GenSkol ty) = (env1, GenSkol ty1)
- where
- (env1, ty1) = tidyOpenType env ty
- tidy_skol_info env info = (env, info)
-
----------------
tidyKind :: TidyEnv -> Kind -> (TidyEnv, Kind)
tidyKind env k = tidyOpenType env k
\end{code}
+%************************************************************************
+%* *
+ Tidying coercions
+%* *
+%************************************************************************
+
+\begin{code}
+
+tidyCo :: TidyEnv -> Coercion -> Coercion
+tidyCo env@(_, subst) co
+ = go co
+ where
+ go (Refl ty) = Refl (tidyType env ty)
+ go (TyConAppCo tc cos) = let args = map go cos
+ in args `seqList` TyConAppCo tc args
+ go (AppCo co1 co2) = (AppCo $! go co1) $! go co2
+ go (ForAllCo tv co) = ForAllCo tvp $! (tidyCo envp co)
+ where
+ (envp, tvp) = tidyTyVarBndr env tv
+ go (CoVarCo cv) = case lookupVarEnv subst cv of
+ Nothing -> CoVarCo cv
+ Just cv' -> CoVarCo cv'
+ go (AxiomInstCo con cos) = let args = tidyCos env cos
+ in args `seqList` AxiomInstCo con args
+ go (UnsafeCo ty1 ty2) = (UnsafeCo $! tidyType env ty1) $! tidyType env ty2
+ go (SymCo co) = SymCo $! go co
+ go (TransCo co1 co2) = (TransCo $! go co1) $! go co2
+ go (NthCo d co) = NthCo d $! go co
+ go (InstCo co ty) = (InstCo $! go co) $! tidyType env ty
+
+tidyCos :: TidyEnv -> [Coercion] -> [Coercion]
+tidyCos env = map (tidyCo env)
+
+\end{code}
%************************************************************************
%* *
| isTcTyVar tv = isSkolemTyVar tv
| otherwise = True
-isTyConableTyVar, isSkolemTyVar, isExistentialTyVar,
+isTyConableTyVar, isSkolemTyVar, isOverlappableTyVar,
isMetaTyVar :: TcTyVar -> Bool
isTyConableTyVar tv
-- not a SigTv
= ASSERT( isTcTyVar tv)
case tcTyVarDetails tv of
- MetaTv (SigTv _) _ -> False
- _ -> True
+ MetaTv SigTv _ -> False
+ _ -> True
isSkolemTyVar tv
= ASSERT2( isTcTyVar tv, ppr tv )
case tcTyVarDetails tv of
- SkolemTv {} -> True
- FlatSkol {} -> True
- MetaTv {} -> False
+ SkolemTv {} -> True
+ FlatSkol {} -> True
+ RuntimeUnk {} -> True
+ MetaTv {} -> False
-isExistentialTyVar tv -- Existential type variable, bound by a pattern
+isOverlappableTyVar tv
= ASSERT( isTcTyVar tv )
case tcTyVarDetails tv of
- SkolemTv (PatSkol {}) -> True
- _ -> False
+ SkolemTv overlappable -> overlappable
+ _ -> False
isMetaTyVar tv
= ASSERT2( isTcTyVar tv, ppr tv )
isSigTyVar tv
= ASSERT( isTcTyVar tv )
case tcTyVarDetails tv of
- MetaTv (SigTv _) _ -> True
- _ -> False
+ MetaTv SigTv _ -> True
+ _ -> False
metaTvRef :: TyVar -> IORef MetaDetails
metaTvRef tv
isIndirect (Indirect _) = True
isIndirect _ = False
-isRuntimeUnk :: TyVar -> Bool
-isRuntimeUnk x | isTcTyVar x
- , SkolemTv RuntimeUnkSkol <- tcTyVarDetails x = True
- | otherwise = False
-
-isUnk :: TyVar -> Bool
-isUnk x | isTcTyVar x
- , SkolemTv UnkSkol <- tcTyVarDetails x = True
- | otherwise = False
+isRuntimeUnkSkol :: TyVar -> Bool
+-- Called only in TcErrors; see Note [Runtime skolems] there
+isRuntimeUnkSkol x
+ | isTcTyVar x, RuntimeUnk <- tcTyVarDetails x = True
+ | otherwise = False
\end{code}
isTauTy (PredTy _) = True -- Don't look through source types
isTauTy _ = False
-
isTauTyCon :: TyCon -> Bool
-- Returns False for type synonyms whose expansion is a polytype
isTauTyCon tc
| otherwise = True
---------------
-isRigidTy :: TcType -> Bool
--- A type is rigid if it has no meta type variables in it
-isRigidTy ty = all isImmutableTyVar (varSetElems (tcTyVarsOfType ty))
-
-isRefineableTy :: TcType -> (Bool,Bool)
--- A type should have type refinements applied to it if it has
--- free type variables, and they are all rigid
-isRefineableTy ty = (null tc_tvs, all isImmutableTyVar tc_tvs)
- where
- tc_tvs = varSetElems (tcTyVarsOfType ty)
-
-isRefineablePred :: TcPredType -> Bool
-isRefineablePred pred = not (null tc_tvs) && all isImmutableTyVar tc_tvs
- where
- tc_tvs = varSetElems (tcTyVarsOfPred pred)
-
----------------
-getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
+getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
-- construct a dictionary function name
getDFunTyKey ty | Just ty' <- tcView ty = getDFunTyKey ty'
getDFunTyKey (TyVarTy tv) = getOccName tv
tcSplitForAllTys ty = split ty ty []
where
split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
- split _ (ForAllTy tv ty) tvs
- | not (isCoVar tv) = split ty ty (tv:tvs)
- split orig_ty _ tvs = (reverse tvs, orig_ty)
+ split _ (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
+ split orig_ty _ tvs = (reverse tvs, orig_ty)
tcIsForAllTy :: Type -> Bool
tcIsForAllTy ty | Just ty' <- tcView ty = tcIsForAllTy ty'
-tcIsForAllTy (ForAllTy tv _) = not (isCoVar tv)
-tcIsForAllTy _ = False
+tcIsForAllTy (ForAllTy {}) = True
+tcIsForAllTy _ = False
tcSplitPredFunTy_maybe :: Type -> Maybe (PredType, Type)
-- Split off the first predicate argument from a type
tcSplitPredFunTy_maybe ty | Just ty' <- tcView ty = tcSplitPredFunTy_maybe ty'
-tcSplitPredFunTy_maybe (ForAllTy tv ty)
- | isCoVar tv = Just (coVarPred tv, ty)
tcSplitPredFunTy_maybe (FunTy arg res)
- | Just p <- tcSplitPredTy_maybe arg = Just (p, res)
+ | Just p <- splitPredTy_maybe arg = Just (p, res)
tcSplitPredFunTy_maybe _
= Nothing
tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
-----------------------
-tcSplitDFunTy :: Type -> ([TyVar], Class, [Type])
+tcSplitDFunTy :: Type -> ([TyVar], Int, Class, [Type])
-- Split the type of a dictionary function
-- We don't use tcSplitSigmaTy, because a DFun may (with NDP)
-- have non-Pred arguments, such as
-- df :: forall m. (forall b. Eq b => Eq (m b)) -> C m
tcSplitDFunTy ty
- = case tcSplitForAllTys ty of { (tvs, rho) ->
- case tcSplitDFunHead (drop_pred_tys rho) of { (clas, tys) ->
- (tvs, clas, tys) }}
+ = case tcSplitForAllTys ty of { (tvs, rho) ->
+ case split_dfun_args 0 rho of { (n_theta, tau) ->
+ case tcSplitDFunHead tau of { (clas, tys) ->
+ (tvs, n_theta, clas, tys) }}}
where
- -- Discard the context of the dfun. This can be a mix of
+ -- Count the context of the dfun. This can be a mix of
-- coercion and class constraints; or (in the general NDP case)
-- some other function argument
- drop_pred_tys ty | Just ty' <- tcView ty = drop_pred_tys ty'
- drop_pred_tys (ForAllTy tv ty) = ASSERT( isCoVar tv ) drop_pred_tys ty
- drop_pred_tys (FunTy _ ty) = drop_pred_tys ty
- drop_pred_tys ty = ty
+ split_dfun_args n ty | Just ty' <- tcView ty = split_dfun_args n ty'
+ split_dfun_args n (FunTy _ ty) = split_dfun_args (n+1) ty
+ split_dfun_args n ty = (n, ty)
tcSplitDFunHead :: Type -> (Class, [Type])
tcSplitDFunHead tau
- = case tcSplitPredTy_maybe tau of
+ = case splitPredTy_maybe tau of
Just (ClassP clas tys) -> (clas, tys)
_ -> pprPanic "tcSplitDFunHead" (ppr tau)
-- Used in Haskell-98 mode, for the argument types of an instance head
-- These must be a constructor applied to type variable arguments
tcInstHeadTyAppAllTyVars ty
+ | Just ty' <- tcView ty -- Look through synonyms
+ = tcInstHeadTyAppAllTyVars ty'
+ | otherwise
= case ty of
TyConApp _ tys -> ok tys
FunTy arg res -> ok [arg, res]
%* *
%************************************************************************
-\begin{code}
-evVarPred :: EvVar -> PredType
-evVarPred var
- = case tcSplitPredTy_maybe (varType var) of
- Just pred -> pred
- Nothing -> pprPanic "evVarPred" (ppr var <+> ppr (varType var))
-
-tcSplitPredTy_maybe :: Type -> Maybe PredType
- -- Returns Just for predicates only
-tcSplitPredTy_maybe ty | Just ty' <- tcView ty = tcSplitPredTy_maybe ty'
-tcSplitPredTy_maybe (PredTy p) = Just p
-tcSplitPredTy_maybe _ = Nothing
-
-predTyUnique :: PredType -> Unique
-predTyUnique (IParam n _) = getUnique (ipNameName n)
-predTyUnique (ClassP clas _) = getUnique clas
-predTyUnique (EqPred a b) = pprPanic "predTyUnique" (ppr (EqPred a b))
-\end{code}
-
-
---------------------- Dictionary types ---------------------------------
-
-\begin{code}
-mkClassPred :: Class -> [Type] -> PredType
-mkClassPred clas tys = ClassP clas tys
-
-isClassPred :: PredType -> Bool
-isClassPred (ClassP _ _) = True
-isClassPred _ = False
-
-isTyVarClassPred :: PredType -> Bool
-isTyVarClassPred (ClassP _ tys) = all tcIsTyVarTy tys
-isTyVarClassPred _ = False
-
-getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
-getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
-getClassPredTys_maybe _ = Nothing
+Superclasses
-getClassPredTys :: PredType -> (Class, [Type])
-getClassPredTys (ClassP clas tys) = (clas, tys)
-getClassPredTys _ = panic "getClassPredTys"
-
-mkDictTy :: Class -> [Type] -> Type
-mkDictTy clas tys = mkPredTy (ClassP clas tys)
-
-
-
-isDictLikeTy :: Type -> Bool
--- Note [Dictionary-like types]
-isDictLikeTy ty | Just ty' <- tcView ty = isDictTy ty'
-isDictLikeTy (PredTy p) = isClassPred p
-isDictLikeTy (TyConApp tc tys)
- | isTupleTyCon tc = all isDictLikeTy tys
-isDictLikeTy _ = False
-\end{code}
-
-Note [Dictionary-like types]
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Being "dictionary-like" means either a dictionary type or a tuple thereof.
-In GHC 6.10 we build implication constraints which construct such tuples,
-and if we land up with a binding
- t :: (C [a], Eq [a])
- t = blah
-then we want to treat t as cheap under "-fdicts-cheap" for example.
-(Implication constraints are normally inlined, but sadly not if the
-occurrence is itself inside an INLINE function! Until we revise the
-handling of implication constraints, that is.) This turned out to
-be important in getting good arities in DPH code. Example:
-
- class C a
- class D a where { foo :: a -> a }
- instance C a => D (Maybe a) where { foo x = x }
-
- bar :: (C a, C b) => a -> b -> (Maybe a, Maybe b)
- {-# INLINE bar #-}
- bar x y = (foo (Just x), foo (Just y))
-
-Then 'bar' should jolly well have arity 4 (two dicts, two args), but
-we ended up with something like
- bar = __inline_me__ (\d1,d2. let t :: (D (Maybe a), D (Maybe b)) = ...
- in \x,y. <blah>)
-
-This is all a bit ad-hoc; eg it relies on knowing that implication
-constraints build tuples.
-
---------------------- Implicit parameters ---------------------------------
-
-\begin{code}
-mkIPPred :: IPName Name -> Type -> PredType
-mkIPPred ip ty = IParam ip ty
-
-isIPPred :: PredType -> Bool
-isIPPred (IParam _ _) = True
-isIPPred _ = False
-\end{code}
-
---------------------- Equality predicates ---------------------------------
\begin{code}
-substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)]
-substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty)
- | (tv,ty) <- eq_spec]
+mkMinimalBySCs :: [PredType] -> [PredType]
+-- Remove predicates that can be deduced from others by superclasses
+mkMinimalBySCs ptys = [ ploc | ploc <- ptys
+ , ploc `not_in_preds` rec_scs ]
+ where
+ rec_scs = concatMap trans_super_classes ptys
+ not_in_preds p ps = null (filter (eqPred p) ps)
+ trans_super_classes (ClassP cls tys) = transSuperClasses cls tys
+ trans_super_classes _other_pty = []
+
+transSuperClasses :: Class -> [Type] -> [PredType]
+transSuperClasses cls tys
+ = foldl (\pts p -> trans_sc p ++ pts) [] $
+ immSuperClasses cls tys
+ where trans_sc :: PredType -> [PredType]
+ trans_sc this_pty@(ClassP cls tys)
+ = foldl (\pts p -> trans_sc p ++ pts) [this_pty] $
+ immSuperClasses cls tys
+ trans_sc pty = [pty]
+
+immSuperClasses :: Class -> [Type] -> [PredType]
+immSuperClasses cls tys
+ = substTheta (zipTopTvSubst tyvars tys) sc_theta
+ where (tyvars,sc_theta,_,_) = classBigSig cls
\end{code}
isOverloadedTy :: Type -> Bool
-- Yes for a type of a function that might require evidence-passing
-- Used only by bindLocalMethods
--- NB: be sure to check for type with an equality predicate; hence isCoVar
isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
-isOverloadedTy (ForAllTy tv ty) = isCoVar tv || isOverloadedTy ty
-isOverloadedTy (FunTy a _) = isPredTy a
-isOverloadedTy _ = False
-
-isPredTy :: Type -> Bool -- Belongs in TcType because it does
- -- not look through newtypes, or predtypes (of course)
-isPredTy ty | Just ty' <- tcView ty = isPredTy ty'
-isPredTy (PredTy _) = True
-isPredTy _ = False
+isOverloadedTy (ForAllTy _ ty) = isOverloadedTy ty
+isOverloadedTy (FunTy a _) = isPredTy a
+isOverloadedTy _ = False
\end{code}
\begin{code}
tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty
tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res
tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg
-tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar)
- `unionVarSet` tcTyVarsOfTyVar tyvar
+tcTyVarsOfType (ForAllTy tyvar ty) = tcTyVarsOfType ty `delVarSet` tyvar
-- We do sometimes quantify over skolem TcTyVars
-tcTyVarsOfTyVar :: TcTyVar -> TyVarSet
-tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv)
- | otherwise = emptyVarSet
-
tcTyVarsOfTypes :: [Type] -> TyVarSet
tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys
tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2
\end{code}
-Note [Silly type synonym]
-~~~~~~~~~~~~~~~~~~~~~~~~~
-Consider
- type T a = Int
-What are the free tyvars of (T x)? Empty, of course!
-Here's the example that Ralf Laemmel showed me:
- foo :: (forall a. C u a -> C u a) -> u
- mappend :: Monoid u => u -> u -> u
-
- bar :: Monoid u => u
- bar = foo (\t -> t `mappend` t)
-We have to generalise at the arg to f, and we don't
-want to capture the constraint (Monad (C u a)) because
-it appears to mention a. Pretty silly, but it was useful to him.
-
-exactTyVarsOfType is used by the type checker to figure out exactly
-which type variables are mentioned in a type. It's also used in the
-smart-app checking code --- see TcExpr.tcIdApp
-
-On the other hand, consider a *top-level* definition
- f = (\x -> x) :: T a -> T a
-If we don't abstract over 'a' it'll get fixed to GHC.Prim.Any, and then
-if we have an application like (f "x") we get a confusing error message
-involving Any. So the conclusion is this: when generalising
- - at top level use tyVarsOfType
- - in nested bindings use exactTyVarsOfType
-See Trac #1813 for example.
-
-\begin{code}
-exactTyVarsOfType :: TcType -> TyVarSet
--- Find the free type variables (of any kind)
--- but *expand* type synonyms. See Note [Silly type synonym] above.
-exactTyVarsOfType ty
- = go ty
- where
- go ty | Just ty' <- tcView ty = go ty' -- This is the key line
- go (TyVarTy tv) = unitVarSet tv
- go (TyConApp _ tys) = exactTyVarsOfTypes tys
- go (PredTy ty) = go_pred ty
- go (FunTy arg res) = go arg `unionVarSet` go res
- go (AppTy fun arg) = go fun `unionVarSet` go arg
- go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar
- `unionVarSet` go_tv tyvar
-
- go_pred (IParam _ ty) = go ty
- go_pred (ClassP _ tys) = exactTyVarsOfTypes tys
- go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2
-
- go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar)
- | otherwise = emptyVarSet
-
-exactTyVarsOfTypes :: [TcType] -> TyVarSet
-exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys
-\end{code}
-
Find the free tycons and classes of a type. This is used in the front
end of the compiler.
\begin{code}
-tyClsNamesOfType :: Type -> NameSet
-tyClsNamesOfType (TyVarTy _) = emptyNameSet
-tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
-tyClsNamesOfType (PredTy (IParam _ ty)) = tyClsNamesOfType ty
-tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
-tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2
-tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
-tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
-tyClsNamesOfType (ForAllTy _ ty) = tyClsNamesOfType ty
-
-tyClsNamesOfTypes :: [Type] -> NameSet
-tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
-
-tyClsNamesOfDFunHead :: Type -> NameSet
+orphNamesOfType :: Type -> NameSet
+orphNamesOfType ty | Just ty' <- tcView ty = orphNamesOfType ty'
+ -- Look through type synonyms (Trac #4912)
+orphNamesOfType (TyVarTy _) = emptyNameSet
+orphNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon)
+ `unionNameSets` orphNamesOfTypes tys
+orphNamesOfType (PredTy (IParam _ ty)) = orphNamesOfType ty
+orphNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl)
+ `unionNameSets` orphNamesOfTypes tys
+orphNamesOfType (PredTy (EqPred ty1 ty2)) = orphNamesOfType ty1
+ `unionNameSets` orphNamesOfType ty2
+orphNamesOfType (FunTy arg res) = orphNamesOfType arg `unionNameSets` orphNamesOfType res
+orphNamesOfType (AppTy fun arg) = orphNamesOfType fun `unionNameSets` orphNamesOfType arg
+orphNamesOfType (ForAllTy _ ty) = orphNamesOfType ty
+
+orphNamesOfTypes :: [Type] -> NameSet
+orphNamesOfTypes tys = foldr (unionNameSets . orphNamesOfType) emptyNameSet tys
+
+orphNamesOfDFunHead :: Type -> NameSet
-- Find the free type constructors and classes
-- of the head of the dfun instance type
-- The 'dfun_head_type' is because of
-- instance Foo a => Baz T where ...
-- The decl is an orphan if Baz and T are both not locally defined,
-- even if Foo *is* locally defined
-tyClsNamesOfDFunHead dfun_ty
+orphNamesOfDFunHead dfun_ty
= case tcSplitSigmaTy dfun_ty of
- (_, _, head_ty) -> tyClsNamesOfType head_ty
+ (_, _, head_ty) -> orphNamesOfType head_ty
+
+orphNamesOfCo :: Coercion -> NameSet
+orphNamesOfCo (Refl ty) = orphNamesOfType ty
+orphNamesOfCo (TyConAppCo tc cos) = unitNameSet (getName tc) `unionNameSets` orphNamesOfCos cos
+orphNamesOfCo (AppCo co1 co2) = orphNamesOfCo co1 `unionNameSets` orphNamesOfCo co2
+orphNamesOfCo (ForAllCo _ co) = orphNamesOfCo co
+orphNamesOfCo (CoVarCo _) = emptyNameSet
+orphNamesOfCo (AxiomInstCo con cos) = orphNamesOfCoCon con `unionNameSets` orphNamesOfCos cos
+orphNamesOfCo (UnsafeCo ty1 ty2) = orphNamesOfType ty1 `unionNameSets` orphNamesOfType ty2
+orphNamesOfCo (SymCo co) = orphNamesOfCo co
+orphNamesOfCo (TransCo co1 co2) = orphNamesOfCo co1 `unionNameSets` orphNamesOfCo co2
+orphNamesOfCo (NthCo _ co) = orphNamesOfCo co
+orphNamesOfCo (InstCo co ty) = orphNamesOfCo co `unionNameSets` orphNamesOfType ty
+
+orphNamesOfCos :: [Coercion] -> NameSet
+orphNamesOfCos = foldr (unionNameSets . orphNamesOfCo) emptyNameSet
+
+orphNamesOfCoCon :: CoAxiom -> NameSet
+orphNamesOfCoCon (CoAxiom { co_ax_lhs = ty1, co_ax_rhs = ty2 })
+ = orphNamesOfType ty1 `unionNameSets` orphNamesOfType ty2
\end{code}
being the )
\begin{code}
-tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type, CoercionI)
+tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type, Coercion)
-- (isIOType t) returns Just (IO,t',co)
-- if co : t ~ IO t'
-- returns Nothing otherwise
Just (io_tycon, [io_res_ty])
| io_tycon `hasKey` ioTyConKey
- -> Just (io_tycon, io_res_ty, IdCo ty)
+ -> Just (io_tycon, io_res_ty, mkReflCo ty)
Just (tc, tys)
| not (isRecursiveTyCon tc)
-- Newtypes that require a coercion are ok
-> case tcSplitIOType_maybe ty of
Nothing -> Nothing
- Just (tc, ty', co2) -> Just (tc, ty', co1 `mkTransCoI` co2)
+ Just (tc, ty', co2) -> Just (tc, ty', co1 `mkTransCo` co2)
_ -> Nothing
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