Fix Trac #1746: make rule-matching work properly with Cast expressions

[ghc-hetmet.git] / compiler / specialise / Rules.lhs

diff --git a/compiler/specialise/Rules.lhs b/compiler/specialise/Rules.lhs
index c1d2006..24c4004 100644 (file)
--- a/compiler/specialise/Rules.lhs
+++ b/compiler/specialise/Rules.lhs
@@ -595,11 +595,8 @@ match menv subst (Type ty1) (Type ty2)
   = match_ty menv subst ty1 ty2
 
 match menv subst (Cast e1 co1) (Cast e2 co2)
-  | (from1, to1) <- coercionKind co1
-  , (from2, to2) <- coercionKind co2
-  = do { subst1 <- match_ty menv subst  to1   to2
-       ; subst2 <- match_ty menv subst1 from1 from2
-       ; match menv subst2 e1 e2 }
+  = do { subst1 <- match_ty menv subst co1 co2
+       ; match menv subst1 e1 e2 }
 
 {-     REMOVING OLD CODE: I think that the above handling for let is 
                           better than the stuff here, which looks 
@@ -646,6 +643,8 @@ match_var menv subst@(tv_subst, id_subst, binds) v1 e2
 
                | otherwise     -- No renaming to do on e2, because no free var
                                -- of e2 is in the rnEnvR of the envt
+               -- Note [Matching variable types]
+               -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                -- However, we must match the *types*; e.g.
                --   forall (c::Char->Int) (x::Char). 
                --      f (c x) = "RULE FIRED"