diff options
Diffstat (limited to 'compiler/typecheck/TcHsSyn.hs')
| -rw-r--r-- | compiler/typecheck/TcHsSyn.hs | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/compiler/typecheck/TcHsSyn.hs b/compiler/typecheck/TcHsSyn.hs index 618c3c067b..2589576910 100644 --- a/compiler/typecheck/TcHsSyn.hs +++ b/compiler/typecheck/TcHsSyn.hs @@ -30,7 +30,7 @@ module TcHsSyn ( zonkTyConBinders, emptyZonkEnv, mkEmptyZonkEnv, zonkTcTypeToType, zonkTcTypeToTypes, zonkTyVarOcc, - zonkCoToCo, + zonkCoToCo, zonkSigType, zonkEvBinds, -- * Validity checking @@ -187,6 +187,8 @@ the environment manipulation is tiresome. -- Confused by zonking? See Note [What is zonking?] in TcMType. type UnboundTyVarZonker = TcTyVar -> TcM Type -- How to zonk an unbound type variable + -- The TcTyVar is (a) a MetaTv (b) Flexi and + -- (c) its kind is alrady zonked -- Note [Zonking the LHS of a RULE] -- | A ZonkEnv carries around several bits. @@ -1595,6 +1597,19 @@ zonkTcTypeToTypes env tys = mapM (zonkTcTypeToType env) tys zonkCoToCo :: ZonkEnv -> Coercion -> TcM Coercion zonkCoToCo = mapCoercion zonk_tycomapper +zonkSigType :: TcType -> TcM Type +-- Zonk the type obtained from a user type signature +-- We want to turn any quantified (forall'd) variables into TyVars +-- but we may find some free TcTyVars, and we want to leave them +-- completely alone. They may even have unification variables inside +-- e.g. f (x::a) = ...(e :: a -> a).... +-- The type sig for 'e' mentions a free 'a' which will be a +-- unification SigTv variable. +zonkSigType = zonkTcTypeToType (mkEmptyZonkEnv zonk_unbound_tv) + where + zonk_unbound_tv :: UnboundTyVarZonker + zonk_unbound_tv tv = return (mkTyVarTy tv) + zonkTvSkolemising :: UnboundTyVarZonker -- This variant is used for the LHS of rules -- See Note [Zonking the LHS of a RULE]. |