--------------------------------
-- Instantiation
tcInstTyVar, tcInstTyVars, tcInstType,
- tcSkolTyVar, tcSkolTyVars, tcSkolType,
+ tcSkolType, tcSkolTyVars,
+ tcSkolSigType, tcSkolSigTyVars,
--------------------------------
-- Checking type validity
import VarSet
import VarEnv
import CmdLineOpts ( dopt, DynFlag(..) )
+import UniqSupply ( uniqsFromSupply )
import Util ( nOfThem, isSingleton, equalLength, notNull )
import ListSetOps ( removeDups )
import SrcLoc ( unLoc )
-- tcInstType instantiates the outer-level for-alls of a TcType with
-- fresh (mutable) type variables, splits off the dictionary part,
-- and returns the pieces.
-tcInstType ty
- = case tcSplitForAllTys ty of
- ([], rho) -> -- There may be overloading despite no type variables;
- -- (?x :: Int) => Int -> Int
- let
- (theta, tau) = tcSplitPhiTy rho
- in
- returnM ([], theta, tau)
+tcInstType ty = tc_inst_type (mappM tcInstTyVar) ty
- (tyvars, rho) -> tcInstTyVars tyvars `thenM` \ (tyvars', _, tenv) ->
- let
- (theta, tau) = tcSplitPhiTy (substTy tenv rho)
- in
- returnM (tyvars', theta, tau)
---------------------------------------------
--- Similar functions but for skolem constants
+tcSkolType :: SkolemInfo -> TcType -> TcM ([TcTyVar], TcThetaType, TcType)
+-- Instantiate a type with fresh skolem constants
+tcSkolType info ty = tc_inst_type (tcSkolTyVars info) ty
tcSkolTyVars :: SkolemInfo -> [TyVar] -> TcM [TcTyVar]
-tcSkolTyVars info tyvars = mappM (tcSkolTyVar info) tyvars
-
-tcSkolTyVar :: SkolemInfo -> TyVar -> TcM TcTyVar
-tcSkolTyVar info tyvar
- = do { uniq <- newUnique
- ; let name = setNameUnique (tyVarName tyvar) uniq
- -- See Note [TyVarName]
- ; return (mkTcTyVar name (tyVarKind tyvar)
- (SkolemTv info)) }
+tcSkolTyVars info tyvars
+ = do { us <- newUniqueSupply
+ ; return (zipWith skol_tv tyvars (uniqsFromSupply us)) }
+ where
+ skol_tv tv uniq = mkTcTyVar (setNameUnique (tyVarName tv) uniq)
+ (tyVarKind tv) (SkolemTv info)
+ -- See Note [TyVarName]
+
-tcSkolType :: SkolemInfo -> TcType -> TcM ([TcTyVar], TcThetaType, TcType)
-tcSkolType info ty
+---------------------------------------------
+tcSkolSigType :: SkolemInfo -> Type -> TcM ([TcTyVar], TcThetaType, TcType)
+-- Instantiate a type signature with skolem constants, but
+-- do *not* give them fresh names, because we want the name to
+-- be in the type environment -- it is lexically scoped.
+tcSkolSigType info ty
+ = tc_inst_type (\tvs -> return (tcSkolSigTyVars info tvs)) ty
+
+tcSkolSigTyVars :: SkolemInfo -> [TyVar] -> [TcTyVar]
+tcSkolSigTyVars info tyvars = [ mkTcTyVar (tyVarName tv) (tyVarKind tv) (SkolemTv info)
+ | tv <- tyvars ]
+
+-----------------------
+tc_inst_type :: ([TyVar] -> TcM [TcTyVar]) -- How to instantiate the type variables
+ -> TcType -- Type to instantiate
+ -> TcM ([TcTyVar], TcThetaType, TcType) -- Result
+tc_inst_type inst_tyvars ty
= case tcSplitForAllTys ty of
- ([], rho) -> let
+ ([], rho) -> let -- There may be overloading despite no type variables;
+ -- (?x :: Int) => Int -> Int
(theta, tau) = tcSplitPhiTy rho
in
- returnM ([], theta, tau)
+ return ([], theta, tau)
- (tyvars, rho) -> tcSkolTyVars info tyvars `thenM` \ tyvars' ->
- let
- tenv = zipTopTvSubst tyvars (mkTyVarTys tyvars')
- (theta, tau) = tcSplitPhiTy (substTy tenv rho)
- in
- returnM (tyvars', theta, tau)
+ (tyvars, rho) -> do { tyvars' <- inst_tyvars tyvars
+
+ ; let tenv = zipTopTvSubst tyvars (mkTyVarTys tyvars')
+ -- Either the tyvars are freshly made, by inst_tyvars,
+ -- or (in the call from tcSkolSigType) any nested foralls
+ -- have different binders. Either way, zipTopTvSubst is ok
+
+ ; let (theta, tau) = tcSplitPhiTy (substTy tenv rho)
+ ; return (tyvars', theta, tau) }
\end{code}
\begin{code}
zonkQuantifiedTyVar :: TcTyVar -> TcM TyVar
-- zonkQuantifiedTyVar is applied to the a TcTyVar when quantifying over it.
--- It might be a meta TyVar, in which case we freeze it inot ano ordinary TyVar.
+-- It might be a meta TyVar, in which case we freeze it into an ordinary TyVar.
-- When we do this, we also default the kind -- see notes with Kind.defaultKind
-- The meta tyvar is updated to point to the new regular TyVar. Now any
-- bound occurences of the original type variable will get zonked to
go (TyConApp tycon tys) = mappM go tys `thenM` \ tys' ->
returnM (TyConApp tycon tys')
- go (NewTcApp tycon tys) = mappM go tys `thenM` \ tys' ->
- returnM (NewTcApp tycon tys')
-
go (NoteTy (SynNote ty1) ty2) = go ty1 `thenM` \ ty1' ->
go ty2 `thenM` \ ty2' ->
returnM (NoteTy (SynNote ty1') ty2')
-> Bool -- Consult the type refinement?
-> TcTyVar -> TcM TcType
zonkTyVar unbound_var_fn rflag tyvar
- | not (isTcTyVar tyvar) -- This can happen when
- -- zonking a forall type, when the bound type variable
- -- needn't be mutable
+ | not (isTcTyVar tyvar) -- When zonking (forall a. ...a...), the occurrences of
+ -- the quantified variable a are TyVars not TcTyVars
= returnM (TyVarTy tyvar)
| otherwise
-- Rank is allowed rank for function args
-- No foralls otherwise
-check_tau_type rank ubx_tup ty@(ForAllTy _ _) = failWithTc (forAllTyErr ty)
-check_tau_type rank ubx_tup (PredTy sty) = getDOpts `thenM` \ dflags ->
- check_source_ty dflags TypeCtxt sty
+check_tau_type rank ubx_tup ty@(ForAllTy _ _) = failWithTc (forAllTyErr ty)
+check_tau_type rank ubx_tup ty@(FunTy (PredTy _) _) = failWithTc (forAllTyErr ty)
+ -- Reject e.g. (Maybe (?x::Int => Int)), with a decent error message
+
+-- Naked PredTys don't usually show up, but they can as a result of
+-- {-# SPECIALISE instance Ord Char #-}
+-- The Right Thing would be to fix the way that SPECIALISE instance pragmas
+-- are handled, but the quick thing is just to permit PredTys here.
+check_tau_type rank ubx_tup (PredTy sty) = getDOpts `thenM` \ dflags ->
+ check_source_ty dflags TypeCtxt sty
+
check_tau_type rank ubx_tup (TyVarTy _) = returnM ()
check_tau_type rank ubx_tup ty@(FunTy arg_ty res_ty)
= check_poly_type rank UT_NotOk arg_ty `thenM_`
check_tau_type rank ubx_tup (NoteTy other_note ty)
= check_tau_type rank ubx_tup ty
-check_tau_type rank ubx_tup (NewTcApp tc tys)
- = mappM_ check_arg_type tys
-
check_tau_type rank ubx_tup ty@(TyConApp tc tys)
| isSynTyCon tc
= -- NB: Type.mkSynTy builds a TyConApp (not a NoteTy) for an unsaturated
ubx_tup_msg = ubxArgTyErr ty
----------------------------------------
-forAllTyErr ty = ptext SLIT("Illegal polymorphic type:") <+> ppr ty
+forAllTyErr ty = ptext SLIT("Illegal polymorphic or qualified type:") <+> ppr ty
unliftedArgErr ty = ptext SLIT("Illegal unlifted type argument:") <+> ppr ty
ubxArgTyErr ty = ptext SLIT("Illegal unboxed tuple type as function argument:") <+> ppr ty
kindErr kind = ptext SLIT("Expecting an ordinary type, but found a type of kind") <+> ppr kind
projects / ghc-hetmet.git / blobdiff