Don't pin a register for gc_thread on SPARC.

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

diff --git a/compiler/typecheck/TcSimplify.lhs b/compiler/typecheck/TcSimplify.lhs
index 98e5aa5..ad7e5c2 100644 (file)
--- a/compiler/typecheck/TcSimplify.lhs
+++ b/compiler/typecheck/TcSimplify.lhs
@@ -710,13 +710,6 @@ tcSimplifyInfer doc tau_tvs wanted
                -- irreds2 will be empty.  But we don't want to generalise over b!
        ; let preds2 = fdPredsOfInsts irreds2   -- irreds2 is zonked
              qtvs   = grow preds2 tau_tvs2 `minusVarSet` oclose preds2 gbl_tvs2
-               ---------------------------------------------------
-               -- BUG WARNING: there's a nasty bug lurking here
-               -- fdPredsOfInsts may return preds that mention variables quantified in
-               -- one of the implication constraints in irreds2; and that is clearly wrong:
-               -- we might quantify over too many variables through accidental capture
-               ---------------------------------------------------
-
        ; let (free, irreds3) = partition (isFreeWhenInferring qtvs) irreds2
        ; extendLIEs free
 
@@ -1023,17 +1016,16 @@ makeImplicationBind loc all_tvs
                     <.> mkWpTyApps eq_cotvs
                     <.> mkWpTyApps (mkTyVarTys all_tvs)
              bind | [dict_irred_id] <- dict_irred_ids  
-                   = mkVarBind dict_irred_id rhs
+                   = VarBind dict_irred_id rhs
                   | otherwise        
-                   = L span $ 
-                     PatBind { pat_lhs = lpat
+                   = PatBind { pat_lhs = lpat
                             , pat_rhs = unguardedGRHSs rhs 
                             , pat_rhs_ty = hsLPatType lpat
                             , bind_fvs = placeHolderNames 
                              }
 
        ; traceTc $ text "makeImplicationBind" <+> ppr implic_inst
-       ; return ([implic_inst], unitBag bind) 
+       ; return ([implic_inst], unitBag (L span bind)) 
         }
 
 -----------------------------------------------------------
@@ -1289,7 +1281,7 @@ tcSimplifySuperClasses loc this givens sc_wanteds
   = do { traceTc (text "tcSimplifySuperClasses")
        ; (irreds,binds1) <- checkLoop env sc_wanteds
        ; let (tidy_env, tidy_irreds) = tidyInsts irreds
-       ; reportNoInstances tidy_env (Just (loc, givens)) tidy_irreds
+       ; reportNoInstances tidy_env (Just (loc, givens)) [] tidy_irreds
        ; return binds1 }
   where
     env =  RedEnv { red_doc = pprInstLoc loc, 
@@ -2361,7 +2353,11 @@ reduceImplication env
               eq_cotvs = map instToVar extra_eq_givens
              dict_ids = map instToId  extra_dict_givens 
 
-              co         = mkWpTyLams tvs
+                        -- Note [Always inline implication constraints]
+              wrap_inline | null dict_ids = idHsWrapper
+                          | otherwise    = WpInline
+              co         = wrap_inline
+                           <.> mkWpTyLams tvs
                            <.> mkWpTyLams eq_cotvs
                            <.> mkWpLams dict_ids
                            <.> WpLet (binds `unionBags` bind)
@@ -2373,15 +2369,12 @@ reduceImplication env
                            . filter (not . isEqInst) 
                            $ wanteds
               payload    = mkBigLHsTup dict_bndrs
+
        
        ; traceTc (vcat [text "reduceImplication" <+> ppr name,
                         ppr simpler_implic_insts,
                         text "->" <+> ppr rhs])
-       ; return (unitBag (L loc (VarBind { var_id= instToId orig_implic
-                                         , var_rhs = rhs
-                                         , var_inline = not (null dict_ids) }
-                               -- See Note [Always inline implication constraints]
-                         )),
+       ; return (unitBag (L loc (VarBind (instToId orig_implic) rhs)),
                  simpler_implic_insts)
        } 
     }
@@ -2987,7 +2980,8 @@ tcSimplifyDeriv orig tyvars theta
        ; (irreds, _) <- tryHardCheckLoop doc wanteds
 
        ; let (tv_dicts, others) = partition ok irreds
-       ; addNoInstanceErrs others
+             (tidy_env, tidy_insts) = tidyInsts others
+        ; reportNoInstances tidy_env Nothing [alt_fix] tidy_insts
        -- See Note [Exotic derived instance contexts] in TcMType
 
        ; let rev_env = zipTopTvSubst tvs (mkTyVarTys tyvars)
@@ -3001,6 +2995,8 @@ tcSimplifyDeriv orig tyvars theta
 
     ok dict | isDict dict = validDerivPred (dictPred dict)
            | otherwise   = False
+    alt_fix = vcat [ptext (sLit "use a standalone 'deriving instance' declaration instead,"),
+                    ptext (sLit "so you can specify the instance context yourself")]
 \end{code}
 
 
@@ -3015,7 +3011,7 @@ tcSimplifyDefault :: ThetaType    -- Wanted; has no type variables in it
 tcSimplifyDefault theta = do
     wanteds <- newDictBndrsO DefaultOrigin theta
     (irreds, _) <- tryHardCheckLoop doc wanteds
-    addNoInstanceErrs  irreds
+    addNoInstanceErrs irreds
     if null irreds then
        return ()
      else
@@ -3111,7 +3107,7 @@ addNoInstanceErrs :: [Inst]       -- Wanted (can include implications)
                  -> TcM ()     
 addNoInstanceErrs insts
   = do { let (tidy_env, tidy_insts) = tidyInsts insts
-       ; reportNoInstances tidy_env Nothing tidy_insts }
+       ; reportNoInstances tidy_env Nothing [] tidy_insts }
 
 reportNoInstances 
        :: TidyEnv
@@ -3119,14 +3115,15 @@ reportNoInstances
                        -- Nothing => top level
                        -- Just (d,g) => d describes the construct
                        --               with givens g
+        -> [SDoc]      -- Alternative fix for no-such-instance
        -> [Inst]       -- What is wanted (can include implications)
        -> TcM ()       
 
-reportNoInstances tidy_env mb_what insts 
-  = groupErrs (report_no_instances tidy_env mb_what) insts
+reportNoInstances tidy_env mb_what alt_fix insts 
+  = groupErrs (report_no_instances tidy_env mb_what alt_fix) insts
 
-report_no_instances :: TidyEnv -> Maybe (InstLoc, [Inst]) -> [Inst] -> TcM ()
-report_no_instances tidy_env mb_what insts
+report_no_instances :: TidyEnv -> Maybe (InstLoc, [Inst]) -> [SDoc] -> [Inst] -> TcM ()
+report_no_instances tidy_env mb_what alt_fixes insts
   = do { inst_envs <- tcGetInstEnvs
        ; let (implics, insts1)  = partition isImplicInst insts
             (insts2, overlaps) = partitionWith (check_overlap inst_envs) insts1
@@ -3144,7 +3141,7 @@ report_no_instances tidy_env mb_what insts
     complain_implic inst       -- Recurse!
       = reportNoInstances tidy_env 
                          (Just (tci_loc inst, tci_given inst)) 
-                         (tci_wanted inst)
+                         alt_fixes (tci_wanted inst)
 
     check_overlap :: (InstEnv,InstEnv) -> Inst -> Either Inst SDoc
        -- Right msg  => overlap message
@@ -3192,13 +3189,13 @@ report_no_instances tidy_env mb_what insts
       = vcat [ addInstLoc insts $
               sep [ ptext (sLit "Could not deduce") <+> pprDictsTheta insts
                   , nest 2 $ ptext (sLit "from the context") <+> pprDictsTheta givens]
-            , show_fixes (fix1 loc : fixes2) ]
+            , show_fixes (fix1 loc : fixes2 ++ alt_fixes) ]
 
       | otherwise      -- Top level 
       = vcat [ addInstLoc insts $
               ptext (sLit "No instance") <> plural insts
                    <+> ptext (sLit "for") <+> pprDictsTheta insts
-            , show_fixes fixes2 ]
+            , show_fixes (fixes2 ++ alt_fixes) ]
 
       where
        fix1 loc = sep [ ptext (sLit "add") <+> pprDictsTheta insts