TcId, TcIdSet,
zonkTopBinds, zonkTopDecls, zonkTopExpr,
- zonkId, zonkIdBndr
+ zonkId, zonkTopBndrs
) where
#include "HsVersions.h"
import TcRnMonad
import Type ( Type )
-import TcType ( TcType, tcGetTyVar )
-import TcMType ( zonkTcTypeToType, zonkTcTyVarToTyVar, zonkTcType, zonkTcTyVars )
+import TcType ( TcType, TcTyVar, eqKind, isTypeKind, mkTyVarTy,
+ tcGetTyVar, isAnyTypeKind, mkTyConApp )
+import qualified Type
+import TcMType ( zonkTcTyVarToTyVar, zonkType, zonkTcType, zonkTcTyVars,
+ putTcTyVar )
import TysPrim ( charPrimTy, intPrimTy, floatPrimTy,
doublePrimTy, addrPrimTy
)
import TysWiredIn ( charTy, stringTy, intTy, integerTy,
- mkListTy, mkPArrTy, mkTupleTy, unitTy )
+ mkListTy, mkPArrTy, mkTupleTy, unitTy,
+ voidTy, listTyCon, tupleTyCon )
+import TyCon ( mkPrimTyCon, tyConKind )
+import PrimRep ( PrimRep(VoidRep) )
import CoreSyn ( CoreExpr )
-import Var ( isId, isLocalVar )
+import Name ( getOccName, mkInternalName, mkDerivedTyConOcc )
+import Var ( isId, isLocalVar, tyVarKind )
+import VarSet
import VarEnv
import BasicTypes ( RecFlag(..), Boxity(..), IPName(..), ipNameName, mapIPName )
import Maybes ( orElse )
+import Unique ( Uniquable(..) )
+import SrcLoc ( noSrcLoc )
import Bag
import Outputable
\end{code}
the environment manipulation is tiresome.
\begin{code}
-type ZonkEnv = IdEnv Id
+data ZonkEnv = ZonkEnv (TcType -> TcM Type) -- How to zonk a type
+ (IdEnv Id) -- What variables are in scope
-- Maps an Id to its zonked version; both have the same Name
-- Is only consulted lazily; hence knot-tying
-emptyZonkEnv = emptyVarEnv
+emptyZonkEnv = ZonkEnv zonkTypeZapping emptyVarEnv
extendZonkEnv :: ZonkEnv -> [Id] -> ZonkEnv
-extendZonkEnv env ids = extendVarEnvList env [(id,id) | id <- ids]
+extendZonkEnv (ZonkEnv zonk_ty env) ids
+ = ZonkEnv zonk_ty (extendVarEnvList env [(id,id) | id <- ids])
+
+setZonkType :: ZonkEnv -> (TcType -> TcM Type) -> ZonkEnv
+setZonkType (ZonkEnv _ env) zonk_ty = ZonkEnv zonk_ty env
mkZonkEnv :: [Id] -> ZonkEnv
mkZonkEnv ids = extendZonkEnv emptyZonkEnv ids
--
-- Even without template splices, in module Main, the checking of
-- 'main' is done as a separte chunk.
-zonkIdOcc env id
+zonkIdOcc (ZonkEnv zonk_ty env) id
| isLocalVar id = lookupVarEnv env id `orElse` id
| otherwise = id
-- zonkIdBndr is used *after* typechecking to get the Id's type
-- to its final form. The TyVarEnv give
-zonkIdBndr :: TcId -> TcM Id
-zonkIdBndr id
- = zonkTcTypeToType (idType id) `thenM` \ ty' ->
+zonkIdBndr :: ZonkEnv -> TcId -> TcM Id
+zonkIdBndr env id
+ = zonkTcTypeToType env (idType id) `thenM` \ ty' ->
returnM (setIdType id ty')
+
+zonkIdBndrs :: ZonkEnv -> [TcId] -> TcM [Id]
+zonkIdBndrs env ids = mappM (zonkIdBndr env) ids
+
+zonkTopBndrs :: [TcId] -> TcM [Id]
+zonkTopBndrs ids = zonkIdBndrs emptyZonkEnv ids
\end{code}
zonkBinds env (MonoBind bind sigs is_rec)
= ASSERT( null sigs )
- fixM (\ ~(env1, _) ->
- zonkMonoBinds env1 bind `thenM` \ (new_bind, new_ids) ->
+ fixM (\ ~(_, _, new_ids) ->
let
- env2 = extendZonkEnv env (bagToList new_ids)
+ env1 = extendZonkEnv env (bagToList new_ids)
in
- returnM (env2, mkMonoBind new_bind [] is_rec)
- )
+ zonkMonoBinds env1 bind `thenM` \ (new_bind, new_ids) ->
+ returnM (env1, new_bind, new_ids)
+ ) `thenM` \ (env1, new_bind, _) ->
+ returnM (env1, mkMonoBind new_bind [] is_rec)
---------------------------------------------
zonkMonoBinds :: ZonkEnv -> TcMonoBinds
returnM (PatMonoBind new_pat new_grhss locn, ids)
zonkMonoBinds env (VarMonoBind var expr)
- = zonkIdBndr var `thenM` \ new_var ->
+ = zonkIdBndr env var `thenM` \ new_var ->
zonkExpr env expr `thenM` \ new_expr ->
returnM (VarMonoBind new_var new_expr, unitBag new_var)
zonkMonoBinds env (CoreMonoBind var core_expr)
- = zonkIdBndr var `thenM` \ new_var ->
+ = zonkIdBndr env var `thenM` \ new_var ->
returnM (CoreMonoBind new_var core_expr, unitBag new_var)
zonkMonoBinds env (FunMonoBind var inf ms locn)
- = zonkIdBndr var `thenM` \ new_var ->
+ = zonkIdBndr env var `thenM` \ new_var ->
mappM (zonkMatch env) ms `thenM` \ new_ms ->
returnM (FunMonoBind new_var inf new_ms locn, unitBag new_var)
-- No need to extend tyvar env: the effects are
-- propagated through binding the tyvars themselves
- mappM zonkIdBndr dicts `thenM` \ new_dicts ->
+ zonkIdBndrs env dicts `thenM` \ new_dicts ->
fixM (\ ~(_, _, val_bind_ids) ->
let
env1 = extendZonkEnv (extendZonkEnv env new_dicts)
-- This isn't the binding occurrence of these tyvars
-- but they should *be* tyvars. Hence tcGetTyVar.
in
- zonkIdBndr global `thenM` \ new_global ->
+ zonkIdBndr env global `thenM` \ new_global ->
returnM (new_tyvars, new_global, zonkIdOcc env local)
\end{code}
returnM (GRHS new_guarded locn)
in
mappM zonk_grhs grhss `thenM` \ new_grhss ->
- zonkTcTypeToType ty `thenM` \ new_ty ->
+ zonkTcTypeToType env ty `thenM` \ new_ty ->
returnM (GRHSs new_grhss new_binds new_ty)
\end{code}
= returnM (HsIPVar (mapIPName (zonkIdOcc env) id))
zonkExpr env (HsLit (HsRat f ty))
- = zonkTcTypeToType ty `thenM` \ new_ty ->
+ = zonkTcTypeToType env ty `thenM` \ new_ty ->
returnM (HsLit (HsRat f new_ty))
zonkExpr env (HsLit (HsLitLit lit ty))
- = zonkTcTypeToType ty `thenM` \ new_ty ->
+ = zonkTcTypeToType env ty `thenM` \ new_ty ->
returnM (HsLit (HsLitLit lit new_ty))
zonkExpr env (HsLit lit)
returnM (HsWith new_expr new_binds is_with)
where
zonk_ip_bind (n, e)
- = mapIPNameTc zonkIdBndr n `thenM` \ n' ->
- zonkExpr env e `thenM` \ e' ->
+ = mapIPNameTc (zonkIdBndr env) n `thenM` \ n' ->
+ zonkExpr env e `thenM` \ e' ->
returnM (n', e')
zonkExpr env (HsDo do_or_lc stmts ids ty src_loc)
= zonkStmts env stmts `thenM` \ new_stmts ->
- zonkTcTypeToType ty `thenM` \ new_ty ->
+ zonkTcTypeToType env ty `thenM` \ new_ty ->
returnM (HsDo do_or_lc new_stmts
(zonkIdOccs env ids)
new_ty src_loc)
zonkExpr env (ExplicitList ty exprs)
- = zonkTcTypeToType ty `thenM` \ new_ty ->
+ = zonkTcTypeToType env ty `thenM` \ new_ty ->
mappM (zonkExpr env) exprs `thenM` \ new_exprs ->
returnM (ExplicitList new_ty new_exprs)
zonkExpr env (ExplicitPArr ty exprs)
- = zonkTcTypeToType ty `thenM` \ new_ty ->
+ = zonkTcTypeToType env ty `thenM` \ new_ty ->
mappM (zonkExpr env) exprs `thenM` \ new_exprs ->
returnM (ExplicitPArr new_ty new_exprs)
zonkExpr env (RecordUpdOut expr in_ty out_ty rbinds)
= zonkExpr env expr `thenM` \ new_expr ->
- zonkTcTypeToType in_ty `thenM` \ new_in_ty ->
- zonkTcTypeToType out_ty `thenM` \ new_out_ty ->
+ zonkTcTypeToType env in_ty `thenM` \ new_in_ty ->
+ zonkTcTypeToType env out_ty `thenM` \ new_out_ty ->
zonkRbinds env rbinds `thenM` \ new_rbinds ->
returnM (RecordUpdOut new_expr new_in_ty new_out_ty new_rbinds)
returnM (PArrSeqOut new_expr new_info)
zonkExpr env (HsCCall fun args may_gc is_casm result_ty)
- = mappM (zonkExpr env) args `thenM` \ new_args ->
- zonkTcTypeToType result_ty `thenM` \ new_result_ty ->
+ = mappM (zonkExpr env) args `thenM` \ new_args ->
+ zonkTcTypeToType env result_ty `thenM` \ new_result_ty ->
returnM (HsCCall fun new_args may_gc is_casm new_result_ty)
zonkExpr env (HsSCC lbl expr)
returnM (TyLam new_tyvars new_expr)
zonkExpr env (TyApp expr tys)
- = zonkExpr env expr `thenM` \ new_expr ->
- mappM zonkTcTypeToType tys `thenM` \ new_tys ->
+ = zonkExpr env expr `thenM` \ new_expr ->
+ mappM (zonkTcTypeToType env) tys `thenM` \ new_tys ->
returnM (TyApp new_expr new_tys)
zonkExpr env (DictLam dicts expr)
- = mappM zonkIdBndr dicts `thenM` \ new_dicts ->
+ = zonkIdBndrs env dicts `thenM` \ new_dicts ->
let
env1 = extendZonkEnv env new_dicts
in
- zonkExpr env1 expr `thenM` \ new_expr ->
+ zonkExpr env1 expr `thenM` \ new_expr ->
returnM (DictLam new_dicts new_expr)
zonkExpr env (DictApp expr dicts)
returnM (ResultStmt new_expr locn : new_stmts)
zonkStmts env (ExprStmt expr ty locn : stmts)
- = zonkExpr env expr `thenM` \ new_expr ->
- zonkTcTypeToType ty `thenM` \ new_ty ->
- zonkStmts env stmts `thenM` \ new_stmts ->
+ = zonkExpr env expr `thenM` \ new_expr ->
+ zonkTcTypeToType env ty `thenM` \ new_ty ->
+ zonkStmts env stmts `thenM` \ new_stmts ->
returnM (ExprStmt new_expr new_ty locn : new_stmts)
zonkStmts env (LetStmt binds : stmts)
returnM (ParPat new_p, ids)
zonkPat env (WildPat ty)
- = zonkTcTypeToType ty `thenM` \ new_ty ->
+ = zonkTcTypeToType env ty `thenM` \ new_ty ->
returnM (WildPat new_ty, emptyBag)
zonkPat env (VarPat v)
- = zonkIdBndr v `thenM` \ new_v ->
+ = zonkIdBndr env v `thenM` \ new_v ->
returnM (VarPat new_v, unitBag new_v)
zonkPat env (LazyPat pat)
returnM (LazyPat new_pat, ids)
zonkPat env (AsPat n pat)
- = zonkIdBndr n `thenM` \ new_n ->
+ = zonkIdBndr env n `thenM` \ new_n ->
zonkPat env pat `thenM` \ (new_pat, ids) ->
returnM (AsPat new_n new_pat, new_n `consBag` ids)
zonkPat env (ListPat pats ty)
- = zonkTcTypeToType ty `thenM` \ new_ty ->
+ = zonkTcTypeToType env ty `thenM` \ new_ty ->
zonkPats env pats `thenM` \ (new_pats, ids) ->
returnM (ListPat new_pats new_ty, ids)
zonkPat env (PArrPat pats ty)
- = zonkTcTypeToType ty `thenM` \ new_ty ->
+ = zonkTcTypeToType env ty `thenM` \ new_ty ->
zonkPats env pats `thenM` \ (new_pats, ids) ->
returnM (PArrPat new_pats new_ty, ids)
returnM (TuplePat new_pats boxed, ids)
zonkPat env (ConPatOut n stuff ty tvs dicts)
- = zonkTcTypeToType ty `thenM` \ new_ty ->
+ = zonkTcTypeToType env ty `thenM` \ new_ty ->
mappM zonkTcTyVarToTyVar tvs `thenM` \ new_tvs ->
- mappM zonkIdBndr dicts `thenM` \ new_dicts ->
+ zonkIdBndrs env dicts `thenM` \ new_dicts ->
let
env1 = extendZonkEnv env new_dicts
in
zonkPat env (LitPat lit) = returnM (LitPat lit, emptyBag)
zonkPat env (SigPatOut pat ty expr)
- = zonkPat env pat `thenM` \ (new_pat, ids) ->
- zonkTcTypeToType ty `thenM` \ new_ty ->
+ = zonkPat env pat `thenM` \ (new_pat, ids) ->
+ zonkTcTypeToType env ty `thenM` \ new_ty ->
zonkExpr env expr `thenM` \ new_expr ->
returnM (SigPatOut new_pat new_ty new_expr, ids)
zonkPat env (NPatOut lit ty expr)
- = zonkTcTypeToType ty `thenM` \ new_ty ->
+ = zonkTcTypeToType env ty `thenM` \ new_ty ->
zonkExpr env expr `thenM` \ new_expr ->
returnM (NPatOut lit new_ty new_expr, emptyBag)
zonkPat env (NPlusKPatOut n k e1 e2)
- = zonkIdBndr n `thenM` \ new_n ->
+ = zonkIdBndr env n `thenM` \ new_n ->
zonkExpr env e1 `thenM` \ new_e1 ->
zonkExpr env e2 `thenM` \ new_e2 ->
returnM (NPlusKPatOut new_n k new_e1 new_e2, unitBag new_n)
zonkPat env (DictPat ds ms)
- = mappM zonkIdBndr ds `thenM` \ new_ds ->
- mappM zonkIdBndr ms `thenM` \ new_ms ->
+ = zonkIdBndrs env ds `thenM` \ new_ds ->
+ zonkIdBndrs env ms `thenM` \ new_ms ->
returnM (DictPat new_ds new_ms,
listToBag new_ds `unionBags` listToBag new_ms)
zonkRules env rs = mappM (zonkRule env) rs
zonkRule env (HsRule name act vars lhs rhs loc)
- = mappM zonk_bndr vars `thenM` \ new_bndrs ->
+ = mappM zonk_bndr vars `thenM` \ new_bndrs ->
+ newMutVar emptyVarSet `thenM` \ unbound_tv_set ->
let
- env1 = extendZonkEnv env (filter isId new_bndrs)
+ env_rhs = extendZonkEnv env (filter isId new_bndrs)
-- Type variables don't need an envt
-- They are bound through the mutable mechanism
+
+ env_lhs = setZonkType env_rhs (zonkTypeCollecting unbound_tv_set)
+ -- We need to gather the type variables mentioned on the LHS so we can
+ -- quantify over them. Example:
+ -- data T a = C
+ --
+ -- foo :: T a -> Int
+ -- foo C = 1
+ --
+ -- {-# RULES "myrule" foo C = 1 #-}
+ --
+ -- After type checking the LHS becomes (foo a (C a))
+ -- and we do not want to zap the unbound tyvar 'a' to (), because
+ -- that limits the applicability of the rule. Instead, we
+ -- want to quantify over it!
+ --
+ -- It's easiest to find the free tyvars here. Attempts to do so earlier
+ -- are tiresome, because (a) the data type is big and (b) finding the
+ -- free type vars of an expression is necessarily monadic operation.
+ -- (consider /\a -> f @ b, where b is side-effected to a)
in
- zonkExpr env1 lhs `thenM` \ new_lhs ->
- zonkExpr env1 rhs `thenM` \ new_rhs ->
- returnM (HsRule name act (map RuleBndr new_bndrs) new_lhs new_rhs loc)
+ zonkExpr env_lhs lhs `thenM` \ new_lhs ->
+ zonkExpr env_rhs rhs `thenM` \ new_rhs ->
+
+ readMutVar unbound_tv_set `thenM` \ unbound_tvs ->
+ let
+ final_bndrs = map RuleBndr (varSetElems unbound_tvs ++ new_bndrs)
-- I hate this map RuleBndr stuff
+ in
+ returnM (HsRule name act final_bndrs new_lhs new_rhs loc)
where
zonk_bndr (RuleBndr v)
- | isId v = zonkIdBndr v
+ | isId v = zonkIdBndr env v
| otherwise = zonkTcTyVarToTyVar v
zonkRule env (IfaceRuleOut fun rule)
= returnM (IfaceRuleOut (zonkIdOcc env fun) rule)
\end{code}
+
+%************************************************************************
+%* *
+\subsection[BackSubst-Foreign]{Foreign exports}
+%* *
+%************************************************************************
+
+\begin{code}
+zonkTcTypeToType :: ZonkEnv -> TcType -> TcM Type
+zonkTcTypeToType (ZonkEnv zonk_ty _) ty = zonk_ty ty
+
+zonkTypeCollecting :: TcRef TyVarSet -> TcType -> TcM Type
+-- This variant collects unbound type variables in a mutable variable
+zonkTypeCollecting unbound_tv_set
+ = zonkType zonk_unbound_tyvar
+ where
+ zonk_unbound_tyvar tv
+ = zonkTcTyVarToTyVar tv `thenM` \ tv' ->
+ readMutVar unbound_tv_set `thenM` \ tv_set ->
+ writeMutVar unbound_tv_set (extendVarSet tv_set tv') `thenM_`
+ return (mkTyVarTy tv')
+
+zonkTypeZapping :: TcType -> TcM Type
+-- This variant is used for everything except the LHS of rules
+-- It zaps unbound type variables to (), or some other arbitrary type
+zonkTypeZapping ty
+ = zonkType zonk_unbound_tyvar ty
+ where
+ -- Zonk a mutable but unbound type variable to an arbitrary type
+ -- We know it's unbound even though we don't carry an environment,
+ -- because at the binding site for a type variable we bind the
+ -- mutable tyvar to a fresh immutable one. So the mutable store
+ -- plays the role of an environment. If we come across a mutable
+ -- type variable that isn't so bound, it must be completely free.
+ zonk_unbound_tyvar tv = putTcTyVar tv (mkArbitraryType tv)
+
+
+-- When the type checker finds a type variable with no binding,
+-- which means it can be instantiated with an arbitrary type, it
+-- usually instantiates it to Void. Eg.
+--
+-- length []
+-- ===>
+-- length Void (Nil Void)
+--
+-- But in really obscure programs, the type variable might have
+-- a kind other than *, so we need to invent a suitably-kinded type.
+--
+-- This commit uses
+-- Void for kind *
+-- List for kind *->*
+-- Tuple for kind *->...*->*
+--
+-- which deals with most cases. (Previously, it only dealt with
+-- kind *.)
+--
+-- In the other cases, it just makes up a TyCon with a suitable
+-- kind. If this gets into an interface file, anyone reading that
+-- file won't understand it. This is fixable (by making the client
+-- of the interface file make up a TyCon too) but it is tiresome and
+-- never happens, so I am leaving it
+
+mkArbitraryType :: TcTyVar -> Type
+-- Make up an arbitrary type whose kind is the same as the tyvar.
+-- We'll use this to instantiate the (unbound) tyvar.
+mkArbitraryType tv
+ | isAnyTypeKind kind = voidTy -- The vastly common case
+ | otherwise = mkTyConApp tycon []
+ where
+ kind = tyVarKind tv
+ (args,res) = Type.splitFunTys kind -- Kinds are simple; use Type.splitFunTys
+
+ tycon | kind `eqKind` tyConKind listTyCon -- *->*
+ = listTyCon -- No tuples this size
+
+ | all isTypeKind args && isTypeKind res
+ = tupleTyCon Boxed (length args) -- *-> ... ->*->*
+
+ | otherwise
+ = pprTrace "Urk! Inventing strangely-kinded void TyCon:" (ppr tc_name $$ ppr kind) $
+ mkPrimTyCon tc_name kind 0 [] VoidRep
+ -- Same name as the tyvar, apart from making it start with a colon (sigh)
+ -- I dread to think what will happen if this gets out into an
+ -- interface file. Catastrophe likely. Major sigh.
+
+ tc_name = mkInternalName (getUnique tv) (mkDerivedTyConOcc (getOccName tv)) noSrcLoc
+\end{code}
--------------------------------
-- Zonking
+ zonkType,
zonkTcTyVar, zonkTcTyVars, zonkTcTyVarsAndFV,
zonkTcType, zonkTcTypes, zonkTcClassConstraints, zonkTcThetaType,
- zonkTcPredType, zonkTcTypeToType, zonkTcTyVarToTyVar, zonkKindEnv,
+ zonkTcPredType, zonkTcTyVarToTyVar, zonkKindEnv,
) where
liftedTypeKind, openTypeKind, defaultKind, superKind,
superBoxity, liftedBoxity, typeKind,
tyVarsOfType, tyVarsOfTypes,
- eqKind, isTypeKind, isAnyTypeKind,
-
+ eqKind, isTypeKind,
isFFIArgumentTy, isFFIImportResultTy
)
import qualified Type ( splitFunTys )
import Subst ( Subst, mkTopTyVarSubst, substTy )
import Class ( Class, DefMeth(..), classArity, className, classBigSig )
-import TyCon ( TyCon, mkPrimTyCon, isSynTyCon, isUnboxedTupleTyCon,
+import TyCon ( TyCon, isSynTyCon, isUnboxedTupleTyCon,
tyConArity, tyConName, tyConKind, tyConTheta,
getSynTyConDefn, tyConDataCons )
import DataCon ( DataCon, dataConWrapId, dataConName, dataConSig, dataConFieldLabels )
import FieldLabel ( fieldLabelName, fieldLabelType )
-import PrimRep ( PrimRep(VoidRep) )
import Var ( TyVar, idType, idName, tyVarKind, tyVarName, isTyVar,
mkTyVar, mkMutTyVar, isMutTyVar, mutTyVarRef )
-- others:
import Generics ( validGenericMethodType )
import TcRnMonad -- TcType, amongst others
-import TysWiredIn ( voidTy, listTyCon, tupleTyCon )
import PrelNames ( cCallableClassKey, cReturnableClassKey, hasKey )
import ForeignCall ( Safety(..) )
import FunDeps ( grow )
import PprType ( pprPred, pprSourceType, pprTheta, pprClassPred )
import Name ( Name, NamedThing(..), setNameUnique,
- mkInternalName, mkDerivedTyConOcc,
mkSystemTvNameEncoded,
)
import VarSet
import BasicTypes ( Boxity(Boxed) )
import CmdLineOpts ( dopt, DynFlag(..) )
-import Unique ( Uniquable(..) )
import SrcLoc ( noSrcLoc )
import Util ( nOfThem, isSingleton, equalLength, notNull )
import ListSetOps ( equivClasses, removeDups )
| tyVarKind kv `eqKind` superBoxity = putTcTyVar kv liftedBoxity
| otherwise = pprPanic "zonkKindEnv" (ppr kv)
-zonkTcTypeToType :: TcType -> TcM Type
-zonkTcTypeToType ty = zonkType zonk_unbound_tyvar ty
- where
- -- Zonk a mutable but unbound type variable to an arbitrary type
- -- We know it's unbound even though we don't carry an environment,
- -- because at the binding site for a type variable we bind the
- -- mutable tyvar to a fresh immutable one. So the mutable store
- -- plays the role of an environment. If we come across a mutable
- -- type variable that isn't so bound, it must be completely free.
- zonk_unbound_tyvar tv = putTcTyVar tv (mkArbitraryType tv)
-
-
--- When the type checker finds a type variable with no binding,
--- which means it can be instantiated with an arbitrary type, it
--- usually instantiates it to Void. Eg.
---
--- length []
--- ===>
--- length Void (Nil Void)
---
--- But in really obscure programs, the type variable might have
--- a kind other than *, so we need to invent a suitably-kinded type.
---
--- This commit uses
--- Void for kind *
--- List for kind *->*
--- Tuple for kind *->...*->*
---
--- which deals with most cases. (Previously, it only dealt with
--- kind *.)
---
--- In the other cases, it just makes up a TyCon with a suitable
--- kind. If this gets into an interface file, anyone reading that
--- file won't understand it. This is fixable (by making the client
--- of the interface file make up a TyCon too) but it is tiresome and
--- never happens, so I am leaving it
-
-mkArbitraryType :: TcTyVar -> Type
--- Make up an arbitrary type whose kind is the same as the tyvar.
--- We'll use this to instantiate the (unbound) tyvar.
-mkArbitraryType tv
- | isAnyTypeKind kind = voidTy -- The vastly common case
- | otherwise = TyConApp tycon []
- where
- kind = tyVarKind tv
- (args,res) = Type.splitFunTys kind -- Kinds are simple; use Type.splitFunTys
-
- tycon | kind `eqKind` tyConKind listTyCon -- *->*
- = listTyCon -- No tuples this size
-
- | all isTypeKind args && isTypeKind res
- = tupleTyCon Boxed (length args) -- *-> ... ->*->*
-
- | otherwise
- = pprTrace "Urk! Inventing strangely-kinded void TyCon:" (ppr tc_name $$ ppr kind) $
- mkPrimTyCon tc_name kind 0 [] VoidRep
- -- Same name as the tyvar, apart from making it start with a colon (sigh)
- -- I dread to think what will happen if this gets out into an
- -- interface file. Catastrophe likely. Major sigh.
-
- tc_name = mkInternalName (getUnique tv) (mkDerivedTyConOcc (getOccName tv)) noSrcLoc
-
-- zonkTcTyVarToTyVar is applied to the *binding* occurrence
-- of a type variable, at the *end* of type checking. It changes
-- the *mutable* type variable into an *immutable* one.
projects / ghc-hetmet.git / commitdiff