Properly ppr InstEqs in wanteds of implication constraints

compiler/typecheck/Inst.lhs

@@ -603,11 +603,14 @@ pprInst i@(EqInst {tci_left = ty1, tci_right = ty2, tci_co = co})
 		(\covar -> text "Wanted" <+> ppr (TyVarTy covar) <+> dcolon <+> ppr (EqPred ty1 ty2))
 		(\co    -> text "Given"  <+> ppr co              <+> dcolon <+> ppr (EqPred ty1 ty2))
 pprInst inst = ppr (instName inst) <+> dcolon 
-		<+> (braces (ppr (instType inst)) $$
+		<+> (braces (ppr (instType inst) <> implicWantedEqs) $$
 		     ifPprDebug implic_stuff)
   where
-    implic_stuff | isImplicInst inst = ppr (tci_reft inst)
-		 | otherwise	     = empty
+    (implic_stuff, implicWantedEqs) 
+      | isImplicInst inst = (ppr (tci_reft inst),
+                            text " &" <+> 
+                            ppr (filter isEqInst (tci_wanted inst)))
+      | otherwise	  = (empty, empty)
 
 pprInstInFull inst@(EqInst {}) = pprInst inst
 pprInstInFull inst = sep [quotes (pprInst inst), nest 2 (pprInstArising inst)]

compiler/typecheck/TcRnTypes.lhs

@@ -663,7 +663,7 @@ data Inst
 	tci_reft   :: Refinement,
 	tci_given  :: [Inst],	    -- Only Dicts and EqInsts
 				    --   (no Methods, LitInsts, ImplicInsts)
-	tci_wanted :: [Inst],	    -- Only Dicts and ImplicInsts
+	tci_wanted :: [Inst],	    -- Only Dicts, EqInst, and ImplicInsts
 				    --   (no Methods or LitInsts)
 
 	tci_loc    :: InstLoc

compiler/typecheck/TcSimplify.lhs

@@ -1022,8 +1022,9 @@ makeImplicationBind loc all_tvs reft
 				                  pat_rhs = unguardedGRHSs rhs, 
 				      	          pat_rhs_ty = tup_ty,
 				      	          bind_fvs = placeHolderNames }
-	; -- pprTrace "Make implic inst" (ppr (implic_inst,irreds,dict_irreds,tup_ty)) $
-	  return ([implic_inst], unitBag (L span bind)) }
+	; traceTc $ text "makeImplicationBind" <+> ppr implic_inst
+	; return ([implic_inst], unitBag (L span bind)) 
+        }
 
 -----------------------------------------------------------
 tryHardCheckLoop :: SDoc
@@ -1848,7 +1849,7 @@ reduceContext env wanteds
 	     text "----",
 	     text "avails" <+> pprAvails avails,
 	     text "improved =" <+> ppr improved,
-	     text "irreds = " <+> ppr irreds,
+	     text "(all) irreds = " <+> ppr all_irreds,
 	     text "binds = " <+> ppr binds,
 	     text "needed givens = " <+> ppr needed_givens,
 	     text "----------------------"