X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypes%2FType.lhs;h=db23582fdbc08e4eda76562f47a3f34d25a627a3;hb=04baa3c1969bdf1c1f39c4383703d9f5acc77d81;hp=d5c00e80704c35d0b4031b5a08998b854c2fc8cf;hpb=c26717e6713bf1037a065ae5d89f98b109f87fab;p=ghc-hetmet.git

diff --git a/compiler/types/Type.lhs b/compiler/types/Type.lhs
index d5c00e8..db23582 100644
--- a/compiler/types/Type.lhs
+++ b/compiler/types/Type.lhs
@@ -55,7 +55,7 @@ module Type (
 	splitTyConApp_maybe, splitTyConApp, 
         splitNewTyConApp_maybe, splitNewTyConApp,
 
-	repType, typePrimRep, coreView, tcView, kindView, rttiView,
+	repType, typePrimRep, coreView, tcView, kindView,
 
 	mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys, 
 	applyTy, applyTys, isForAllTy, dropForAlls,
@@ -130,6 +130,7 @@ import TyCon
 import StaticFlags
 import Util
 import Outputable
+import FastString
 
 import Data.List
 import Data.Maybe	( isJust )
@@ -187,16 +188,6 @@ tcView (TyConApp tc tys) | Just (tenv, rhs, tys') <- tcExpandTyCon_maybe tc tys
 tcView _                 = Nothing
 
 -----------------------------------------------
-rttiView :: Type -> Type
--- Same, but for the RTTI system, which cannot deal with predicates nor polymorphism
-rttiView (ForAllTy _ ty) = rttiView ty
-rttiView (FunTy PredTy{} ty) = rttiView ty
-rttiView ty@TyConApp{} | Just ty' <- coreView ty 
-                           = rttiView ty'
-rttiView (TyConApp tc tys) = mkTyConApp tc (map rttiView tys)
-rttiView ty = ty
-
------------------------------------------------
 {-# INLINE kindView #-}
 kindView :: Kind -> Maybe Kind
 -- C.f. coreView, tcView
@@ -1267,6 +1258,19 @@ extendTvSubstList (TvSubst in_scope env) tvs tys
 -- the types given; but it's just a thunk so with a bit of luck
 -- it'll never be evaluated
 
+-- Note [Generating the in-scope set for a substitution]
+-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+-- If we want to substitute [a -> ty1, b -> ty2] I used to 
+-- think it was enough to generate an in-scope set that includes
+-- fv(ty1,ty2).  But that's not enough; we really should also take the
+-- free vars of the type we are substituting into!  Example:
+--	(forall b. (a,b,x)) [a -> List b]
+-- Then if we use the in-scope set {b}, there is a danger we will rename
+-- the forall'd variable to 'x' by mistake, getting this:
+--	(forall x. (List b, x, x)
+-- Urk!  This means looking at all the calls to mkOpenTvSubst....
+
+
 mkOpenTvSubst :: TvSubstEnv -> TvSubst
 mkOpenTvSubst env = TvSubst (mkInScopeSet (tyVarsOfTypes (varEnvElts env))) env