X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FcoreSyn%2FSubst.lhs;h=c406f926e01698619a8631b0fbfa4d265bd8b25e;hb=eef96a799e366e63b0fb42c97daf7bcb7f1a8677;hp=02ab9fd95b4eb0d71349a6093994cecc7e2efd39;hpb=b3e58b417b2cb47c35fe3006192a01eecf8d09b5;p=ghc-hetmet.git

diff --git a/ghc/compiler/coreSyn/Subst.lhs b/ghc/compiler/coreSyn/Subst.lhs
index 02ab9fd..c406f92 100644
--- a/ghc/compiler/coreSyn/Subst.lhs
+++ b/ghc/compiler/coreSyn/Subst.lhs
@@ -249,6 +249,7 @@ substInScope (Subst in_scope _) = in_scope
 zapSubstEnv :: Subst -> Subst
 zapSubstEnv (Subst in_scope env) = Subst in_scope emptySubstEnv
 
+-- ToDo: add an ASSERT that fvs(subst-result) is already in the in-scope set
 extendSubst :: Subst -> Var -> SubstResult -> Subst
 extendSubst (Subst in_scope env) v r = Subst in_scope (extendSubstEnv env v r)
 
@@ -390,6 +391,7 @@ zipTyEnv tyvars tys
 #endif
   = zip_ty_env tyvars tys emptySubstEnv
 
+-- Later substitutions in the list over-ride earlier ones
 zip_ty_env []       []       env = env
 zip_ty_env (tv:tvs) (ty:tys) env = zip_ty_env tvs tys (extendSubstEnv env tv (DoneTy ty))
 	-- There used to be a special case for when