X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcTyFuns.lhs;h=7bb8680861c023571505e274ba9e7a19100131c7;hb=f4b727487a65e6b611bbaafbd2207bd63a8df706;hp=8b01749214222ff28cf2d8126045430313a5b5df;hpb=da2e18b9ab29131bda1ac8e3962dc50b635589a5;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcTyFuns.lhs b/compiler/typecheck/TcTyFuns.lhs
index 8b01749..7bb8680 100644
--- a/compiler/typecheck/TcTyFuns.lhs
+++ b/compiler/typecheck/TcTyFuns.lhs
@@ -38,7 +38,6 @@ import Bag
 import Outputable
 import SrcLoc	( Located(..) )
 import Maybes
-import MonadUtils
 import FastString
 
 -- standard
@@ -795,18 +794,19 @@ flattenType inst ty = go ty
                      thisRewriteFam : concat args_eqss)
            }
 
-      -- data constructor application => flatten subtypes
+      -- datatype constructor application => flatten subtypes
       -- NB: Special cased for efficiency - could be handled as type application
     go ty@(TyConApp con args)
       | not (isOpenSynTyCon con)   -- don't match oversaturated family apps
       = do { (args', cargs, args_eqss) <- mapAndUnzip3M go args
-           ; if null args_eqss
+           ; let args_eqs = concat args_eqss
+           ; if null args_eqs
              then     -- unchanged, keep the old type with folded synonyms
                return (ty, ty, [])
              else 
                return (mkTyConApp con args', 
                        mkTyConApp con cargs,
-                       concat args_eqss)
+                       args_eqs)
            }
 
       -- function type => flatten subtypes
@@ -849,9 +849,32 @@ flattenType inst ty = go ty
       | otherwise
       = panic "TcTyFuns.flattenType: synonym family in a rank-n type"
 
-      -- we should never see a predicate type
-    go (PredTy _)
-      = panic "TcTyFuns.flattenType: unexpected PredType"
+      -- predicate type => handle like a datatype constructor application
+    go (PredTy (ClassP cls tys))
+      = do { (tys', ctys, tys_eqss) <- mapAndUnzip3M go tys
+           ; let tys_eqs = concat tys_eqss
+           ; if null tys_eqs
+             then     -- unchanged, keep the old type with folded synonyms
+               return (ty, ty, [])
+             else 
+               return (PredTy (ClassP cls tys'), 
+                       PredTy (ClassP cls ctys),
+                       tys_eqs)
+           }
+
+      -- implicit parameter => flatten subtype
+    go ty@(PredTy (IParam ipn ity))
+      = do { (ity', co, eqs) <- go ity
+           ; if null eqs 
+             then return (ty, ty, []) 
+             else return (PredTy (IParam ipn ity'),
+                          PredTy (IParam ipn co),
+                          eqs)
+           }
+
+      -- we should never see a equality
+    go (PredTy (EqPred _ _))
+      = panic "TcTyFuns.flattenType: malformed type"
 
     go _ = panic "TcTyFuns: suppress bogus warning"
 
@@ -1576,10 +1599,9 @@ somethingdifferent message.
 eqInstMisMatch :: Inst -> TcM a
 eqInstMisMatch inst
   = ASSERT( isEqInst inst )
-    setErrCtxt ctxt $ failWithMisMatch ty_act ty_exp
+    setInstCtxt (instLoc inst) $ failWithMisMatch ty_act ty_exp
   where
     (ty_act, ty_exp) = eqInstTys inst
-    InstLoc _ _ ctxt = instLoc   inst
 
 -----------------------
 failWithMisMatch :: TcType -> TcType -> TcM a
@@ -1610,10 +1632,10 @@ misMatchMsg env0 (ty_act, ty_exp)
     open_tcs = [tc | TyConApp tc _ <- [ty_act, ty_exp]
                    , isOpenTyCon tc ]
     pp_open_tc tc = ptext (sLit "NB:") <+> quotes (ppr tc) 
-    	       	    <+> pp_inj <+> ptext (sLit "type function")
-  		  where
-		    pp_inj | isInjectiveTyCon tc = ptext (sLit "is an (injective)")
-		    	   | otherwise           = ptext (sLit "is a (non-injective)")
+    	       	    <+> ptext (sLit "is a type function") <> pp_inj
+	where
+          pp_inj | isInjectiveTyCon tc = empty
+                 | otherwise = ptext (sLit (", and may not be injective"))
 
     ppr_ty :: TidyEnv -> TcType -> (TidyEnv, SDoc, SDoc)
     ppr_ty env ty
@@ -1639,7 +1661,7 @@ It's very confusing to get a message like
      Couldn't match expected type `Depend s'
             against inferred type `Depend s1'
 so pp_open_tc adds:
-       NB: `Depend' is a (non-injective) type function
+       NB: `Depend' is type function, and hence may not be injective
 
 Currently we add this independently for each argument, so we also get
      Couldn't match expected type `a'