From c1d5f86e824145b0d9f6a81e1587504c19a4377b Mon Sep 17 00:00:00 2001
From: Evan Czaplicki <info@elm-lang.org>
Date: Fri, 26 Jul 2013 21:18:44 +0200
Subject: [PATCH] Simplify type error messages

---
 compiler/Type/State.hs | 10 +++-------
 compiler/Type/Unify.hs |  4 ++--
 2 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/compiler/Type/State.hs b/compiler/Type/State.hs
index e1bd0b9..3a920e6 100644
--- a/compiler/Type/State.hs
+++ b/compiler/Type/State.hs
@@ -47,15 +47,11 @@ modifyPool f = modify $ \state -> state { sPool = f (sPool state) }
 addError message t1 t2 =
     modify $ \state -> state { sErrors = err : sErrors state }
   where
-    wordify = P.fsep . map P.text . words 
-    msg = wordify message
-    width = maximum . map length . lines $ render msg
-    spaces = List.replicate (width - 15 - 3) ' '
     err = makeError <$> extraPretty t1 <*> extraPretty t2
     makeError pt1 pt2 =
-        P.vcat [ P.text $ "Type error" ++ spaces ++ "line ???"
-               , P.text (List.replicate width '-')
-               , msg <> P.text "\n"
+        P.vcat [ P.text $ "Type error on line ???"
+               , if null message then empty else P.fsep . map P.text $ words message
+               , P.text " "
                , P.text "   Expected Type:" <+> pt1
                , P.text "     Actual Type:" <+> pt2 <> P.text "\n"
                ]
diff --git a/compiler/Type/Unify.hs b/compiler/Type/Unify.hs
index bcce02b..18b18c2 100644
--- a/compiler/Type/Unify.hs
+++ b/compiler/Type/Unify.hs
@@ -95,7 +95,7 @@ actuallyUnify variable1 variable2 = do
                 | name `elem` ["Int","Float","Char"] -> flexAndUnify variable2
                 | otherwise -> TS.addError "Expecting something comparable (Int, Float, Char, [comparable])." variable1 variable2
 
-            _ -> TS.addError "The following types are not equal" variable1 variable2
+            _ -> TS.addError "" variable1 variable2
 
   case (structure desc1, structure desc2) of
     (Nothing, Nothing) | flex desc1 == Flexible && flex desc1 == Flexible -> merge
@@ -144,5 +144,5 @@ actuallyUnify variable1 variable2 = do
                 eat (x:xs) (y:ys) = eat xs ys
                 eat xs ys = xs
 
-          _ -> TS.addError "The following types are not equal" variable1 variable2
+          _ -> TS.addError "" variable1 variable2