[project @ 2004-08-18 09:33:03 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 b3bea61..b7002f8 100644 (file)
--- a/ghc/compiler/typecheck/TcSimplify.lhs
+++ b/ghc/compiler/typecheck/TcSimplify.lhs
@@ -26,7 +26,7 @@ import TcHsSyn                ( TcId, TcDictBinds, mkHsApp, mkHsTyApp, mkHsDictApp )
 
 import TcRnMonad
 import Inst            ( lookupInst, LookupInstResult(..),
-                         tyVarsOfInst, fdPredsOfInsts, fdPredsOfInst, newDicts,
+                         tyVarsOfInst, fdPredsOfInsts, newDicts, 
                          isDict, isClassDict, isLinearInst, linearInstType,
                          isStdClassTyVarDict, isMethodFor, isMethod,
                          instToId, tyVarsOfInsts,  cloneDict,
@@ -1530,20 +1530,23 @@ 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)
+       preds = [ (dictPred inst, pp_loc)
                | inst <- keysFM avails,
-                 let pp_loc = pprInstLoc (instLoc inst),
-                 pred <- fdPredsOfInst inst
+                 isDict inst,
+                 let pp_loc = pprInstLoc (instLoc inst)
                ]
                -- Avails has all the superclasses etc (good)
                -- It also has all the intermediates of the deduction (good)
                -- It does not have duplicates (good)
                -- NB that (?x::t1) and (?x::t2) will be held separately in avails
                --    so that improve will see them separate
+               --
+               -- Notice that we only look at dicts; LitInsts and Methods will have
+               -- been squished, so their dicts will be in Avails too
        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
@@ -1552,10 +1555,11 @@ tcImprove avails
         mappM_ unify eqns      `thenM_`
        returnM False
   where
-    unify ((qtvs, t1, t2), doc)
+    unify ((qtvs, pairs), doc)
         = addErrCtxt doc                               $
           tcInstTyVars VanillaTv (varSetElems qtvs)    `thenM` \ (_, _, tenv) ->
-          unifyTauTy (substTy tenv t1) (substTy tenv t2)
+          mapM_ (unif_pr tenv) pairs
+    unif_pr tenv (ty1,ty2) =  unifyTauTy (substTy tenv ty1) (substTy tenv ty2)
 \end{code}
 
 The main context-reduction function is @reduce@.  Here's its game plan.