[project @ 2004-08-16 09:53:47 by simonpj]

[ghc-hetmet.git] / ghc / compiler / typecheck / TcSimplify.lhs

diff --git a/ghc/compiler/typecheck/TcSimplify.lhs b/ghc/compiler/typecheck/TcSimplify.lhs
index 2501014..8dba75c 100644 (file)
--- a/ghc/compiler/typecheck/TcSimplify.lhs
+++ b/ghc/compiler/typecheck/TcSimplify.lhs
@@ -1054,7 +1054,7 @@ because the scsel will mess up matching.  Instead we want
        forall dIntegralInt, dNumInt.
        fromIntegral Int Int dIntegralInt dNumInt = id Int
 
-Hence "DontReduce NoSCs"
+Hence "WithoutSCs"
 
 \begin{code}
 tcSimplifyToDicts :: [Inst] -> TcM (TcDictBinds)
@@ -1070,7 +1070,7 @@ tcSimplifyToDicts wanteds
     doc = text "tcSimplifyToDicts"
 
        -- Reduce methods and lits only; stop as soon as we get a dictionary
-    try_me inst        | isDict inst = DontReduce NoSCs        -- See notes above for why NoSCs
+    try_me inst        | isDict inst = KeepDictWithoutSCs      -- See notes above re "WithoutSCs"
                | otherwise   = ReduceMe
 \end{code}
 
@@ -1214,7 +1214,8 @@ data WhatToDo
                        -- produce an error message of any kind.
                        -- It might be quite legitimate such as (Eq a)!
 
- | DontReduce WantSCs          -- Return as irreducible
+ | KeepDictWithoutSCs  -- Return as irreducible; don't add its superclasses
+                       -- Rather specialised: see notes with tcSimplifyToDicts
 
  | DontReduceUnlessConstant    -- Return as irreducible unless it can
                                -- be reduced to a constant in one step
@@ -1529,7 +1530,7 @@ reduceContextWithoutImprovement doc try_me wanteds
 tcImprove :: Avails -> TcM Bool                -- False <=> no change
 -- Perform improvement using all the predicates in Avails
 tcImprove avails
- =  tcGetInstEnvs                      `thenM` \ (home_ie, pkg_ie) ->
+ =  tcGetInstEnvs                      `thenM` \ inst_envs -> 
     let
        preds = [ (pred, pp_loc)
                | inst <- keysFM avails,
@@ -1542,7 +1543,7 @@ tcImprove avails
                -- NB that (?x::t1) and (?x::t2) will be held separately in avails
                --    so that improve will see them separate
        eqns = improve get_insts preds
-       get_insts clas = classInstances home_ie clas ++ classInstances pkg_ie clas
+       get_insts clas = classInstances inst_envs clas
      in
      if null eqns then
        returnM True
@@ -1617,7 +1618,7 @@ reduce stack try_me wanted avails
   | otherwise
   = case try_me wanted of {
 
-      DontReduce want_scs -> addIrred want_scs avails wanted
+      KeepDictWithoutSCs -> addIrred NoSCs avails wanted
 
     ; DontReduceUnlessConstant ->    -- It's irreducible (or at least should not be reduced)
                                     -- First, see if the inst can be reduced to a constant in one step