Fixes to datacon wrappers for indexed data types

[ghc-hetmet.git] / compiler / types / Unify.lhs

diff --git a/compiler/types/Unify.lhs b/compiler/types/Unify.lhs
index 34993ad..f99c56c 100644 (file)
--- a/compiler/types/Unify.lhs
+++ b/compiler/types/Unify.lhs
@@ -7,7 +7,8 @@ module Unify (
        -- Matching of types: 
        --      the "tc" prefix indicates that matching always
        --      respects newtypes (rather than looking through them)
-       tcMatchTys, tcMatchTyX, ruleMatchTyX, tcMatchPreds, MatchEnv(..)
+       tcMatchTy, tcMatchTys, tcMatchTyX, 
+       ruleMatchTyX, tcMatchPreds, MatchEnv(..)
    ) where
 
 #include "HsVersions.h"
@@ -57,10 +58,26 @@ data MatchEnv
        , me_env   :: RnEnv2    -- Renaming envt for nested foralls
        }                       --   In-scope set includes template tyvars
 
+tcMatchTy :: TyVarSet          -- Template tyvars
+         -> Type               -- Template
+         -> Type               -- Target
+         -> Maybe TvSubst      -- One-shot; in principle the template
+                               -- variables could be free in the target
+
+tcMatchTy tmpls ty1 ty2
+  = case match menv emptyTvSubstEnv ty1 ty2 of
+       Just subst_env -> Just (TvSubst in_scope subst_env)
+       Nothing        -> Nothing
+  where
+    menv     = ME { me_tmpls = tmpls, me_env = mkRnEnv2 in_scope }
+    in_scope = mkInScopeSet (tmpls `unionVarSet` tyVarsOfType ty2)
+       -- We're assuming that all the interesting 
+       -- tyvars in tys1 are in tmpls
+
 tcMatchTys :: TyVarSet         -- Template tyvars
-        -> [Type]              -- Template
-        -> [Type]              -- Target
-        -> Maybe TvSubst       -- One-shot; in principle the template
+          -> [Type]            -- Template
+          -> [Type]            -- Target
+          -> Maybe TvSubst     -- One-shot; in principle the template
                                -- variables could be free in the target
 
 tcMatchTys tmpls tys1 tys2