More error message wibbles

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

diff --git a/compiler/typecheck/TcErrors.lhs b/compiler/typecheck/TcErrors.lhs
index b3dfb9c..c30d702 100644 (file)
--- a/compiler/typecheck/TcErrors.lhs
+++ b/compiler/typecheck/TcErrors.lhs
@@ -158,7 +158,7 @@ reportTidyWanteds ctxt unsolved
 reportFlat :: ReportErrCtxt -> [PredType] -> CtOrigin -> TcM ()
 reportFlat ctxt flats origin
   = do { unless (null dicts) $ reportDictErrs ctxt dicts origin
-       ; unless (null eqs)   $ reportEqErrs   ctxt eqs   
+       ; unless (null eqs)   $ reportEqErrs   ctxt eqs   origin
        ; unless (null ips)   $ reportIPErrs   ctxt ips   origin
        ; ASSERT( null others ) return () }
   where
@@ -277,12 +277,17 @@ reportIPErrs ctxt ips orig
 %************************************************************************
 
 \begin{code}
-reportEqErrs :: ReportErrCtxt -> [PredType] -> TcM ()
-reportEqErrs ctxt eqs 
+reportEqErrs :: ReportErrCtxt -> [PredType] -> CtOrigin -> TcM ()
+reportEqErrs ctxt eqs orig
   = mapM_ report_one eqs 
   where
-    report_one (EqPred ty1 ty2) = reportEqErr ctxt ty1 ty2
-    report_one pred             = pprPanic "reportEqErrs" (ppr pred)    
+    report_one (EqPred ty1 ty2) 
+      = do { (env1, extra) <- getWantedEqExtra (cec_tidy ctxt) orig ty1 ty2
+           ; let ctxt' = ctxt { cec_tidy = env1
+                              , cec_extra = cec_extra ctxt $$ extra }
+           ; reportEqErr ctxt' ty1 ty2 }
+    report_one pred 
+      = pprPanic "reportEqErrs" (ppr pred)    
 
 reportEqErr :: ReportErrCtxt -> TcType -> TcType -> TcM ()
 reportEqErr ctxt ty1 ty2
@@ -653,23 +658,24 @@ kindErrorTcS fl ty1 ty2
   = wrapErrTcS        $ 
     setCtFlavorLoc fl $ 
     do { env0 <- tcInitTidyEnv
-       ; let (env1, ty1') = tidyOpenType env0 ty1
-             (env2, ty2') = tidyOpenType env1 ty2
+       ; (env1, extra) <- getEqExtra env0 fl ty1 ty2
+       ; let (env2, ty1') = tidyOpenType env1 ty1
+             (env3, ty2') = tidyOpenType env2 ty2
              ctxt = CEC { cec_encl = []
-                        , cec_extra = empty
-                        , cec_tidy = env2 }
+                        , cec_extra = extra
+                        , cec_tidy = env3 }
        ; reportEqErr ctxt ty1' ty2' }
 
 misMatchErrorTcS :: CtFlavor -> TcType -> TcType -> TcS a
 misMatchErrorTcS fl ty1 ty2
-  = wrapErrTcS            $ 
-    setCtFlavorLocNoEq fl $  -- Don't add the "When matching t1 with t2"
-                            -- part, because it duplciates what we say now
+  = wrapErrTcS        $ 
+    setCtFlavorLoc fl $ 
     do { env0 <- tcInitTidyEnv
        ; let (env1, ty1') = tidyOpenType env0 ty1
              (env2, ty2') = tidyOpenType env1 ty2
              (env3, msg)  = misMatchMsgWithExtras env2 ty1' ty2'
-       ; failWithTcM (env3, inaccessible_msg $$ msg) }
+       ; (env4, extra) <- getEqExtra env3 fl ty1 ty2
+       ; failWithTcM (env4, inaccessible_msg $$ msg $$ extra) }
   where
     inaccessible_msg 
       = case fl of 
@@ -685,13 +691,14 @@ misMatchErrorTcS fl ty1 ty2
 
 occursCheckErrorTcS :: CtFlavor -> TcTyVar -> TcType -> TcS a
 occursCheckErrorTcS fl tv ty
-  = wrapErrTcS           $ 
-    setCtFlavorLoc fl $ 
-    do { env0          <- tcInitTidyEnv
-       ; let (env1, tv') = tidyOpenTyVar env0 tv
+  = wrapErrTcS        $ 
+    setCtFlavorLoc fl $
+    do { env0 <- tcInitTidyEnv
+        ; let (env1, tv') = tidyOpenTyVar env0 tv
              (env2, ty') = tidyOpenType env1 ty
-             extra = sep [ppr tv', char '=', ppr ty']
-       ; failWithTcM (env2, hang msg 2 extra) }
+             extra1 = sep [ppr tv', char '=', ppr ty']
+       ; (env3, extra2) <- getEqExtra env2 fl (mkTyVarTy tv) ty
+       ; failWithTcM (env3, hang msg 2 (extra1 $$ extra2)) }
   where
     msg = text $ "Occurs check: cannot construct the infinite type:"
 
@@ -731,30 +738,33 @@ flattenForAllErrorTcS fl ty _bad_eqs
 %************************************************************************
 
 \begin{code}
-setCtFlavorLocNoEq :: CtFlavor -> TcM a -> TcM a
-setCtFlavorLocNoEq (Wanted  loc) thing = setCtLoc loc thing
-setCtFlavorLocNoEq (Derived loc) thing = setCtLoc loc thing
-setCtFlavorLocNoEq (Given   loc) thing = setCtLoc loc thing
-
 setCtFlavorLoc :: CtFlavor -> TcM a -> TcM a
-setCtFlavorLoc (Wanted  loc) thing = setWantedLoc loc thing
-setCtFlavorLoc (Derived loc) thing = setWantedLoc loc thing
-setCtFlavorLoc (Given   loc) thing = setGivenLoc  loc thing
-
-setWantedLoc :: WantedLoc -> TcM a -> TcM a
-setWantedLoc loc thing_inside 
-  = setCtLoc loc $
-    add_origin (ctLocOrigin loc) $ 
-    thing_inside
-  where
-    add_origin (TypeEqOrigin item) = addErrCtxtM (unifyCtxt item)
-    add_origin orig = addErrCtxt (ptext (sLit "At") <+> ppr orig)
+setCtFlavorLoc (Wanted  loc) thing = setCtLoc loc thing
+setCtFlavorLoc (Derived loc) thing = setCtLoc loc thing
+setCtFlavorLoc (Given   loc) thing = setCtLoc loc thing
+
+getEqExtra :: TidyEnv -> CtFlavor -> TcType -> TcType -> TcM (TidyEnv, SDoc)
+getEqExtra env (Wanted  loc) ty1 ty2 = getWantedEqExtra env (ctLocOrigin loc) ty1 ty2
+getEqExtra env (Derived loc) ty1 ty2 = getWantedEqExtra env (ctLocOrigin loc) ty1 ty2
+getEqExtra env (Given   _)   _   _   = return (env, empty)
+  -- We could print more info, but it seems to be already coming out
+
+getWantedEqExtra :: TidyEnv -> CtOrigin -> TcType -> TcType -> TcM (TidyEnv, SDoc)
+getWantedEqExtra env0 (TypeEqOrigin item) ty1 ty2
+  -- If the types in the error message are the same 
+  -- as the types we are unifying (remember to zonk the latter)
+  -- don't add the extra expected/actual message
+  = do { act <- zonkTcType (uo_actual item)
+       ; exp <- zonkTcType (uo_expected item)
+       ; if (act `tcEqType` ty1 && exp `tcEqType` ty2)
+         || (exp `tcEqType` ty1 && act `tcEqType` ty2)
+         then  
+            return (env0, empty)
+         else do
+       { let (env1, exp') = tidyOpenType env0 exp
+             (env2, act') = tidyOpenType env1     act
+       ; return (env2, mkExpectedActualMsg act' exp') } }
 
-setGivenLoc :: GivenLoc -> TcM a -> TcM a
-setGivenLoc loc thing_inside 
-  = setCtLoc loc $
-    add_origin (ctLocOrigin loc) $ 
-    thing_inside
-  where
-    add_origin skol = addErrCtxt (ptext (sLit "In") <+> pprSkolInfo skol)
+getWantedEqExtra env0 orig _ _ 
+  = return (env0, pprArising orig)
 \end{code}