Ensure that exception message is printed.

frog/corejs.dart

Index: frog/corejs.dart
diff --git a/frog/corejs.dart b/frog/corejs.dart
index 6193659a8853094db044fecffe1310a7317e32df..fd5f1f81efaacd6e7c000457b3ccbce591841819 100644
--- a/frog/corejs.dart
+++ b/frog/corejs.dart
@@ -253,42 +253,58 @@ function $stackTraceOf(e) {
 // Translate a JavaScript exception to a Dart exception
 // TODO(jmesserly): cross browser support. This is Chrome specific.
 function $toDartException(e) {
-  var res = e;
+  function attachStack(dartEx) {
+    // TODO(jmesserly): setting the stack property is not a long term solution.
+    var stack = e.stack;
+    // The stack contains the error message, and the stack is all that is
+    // printed (the exception's toString() is never called).  Attempt to replace
+    // the JS message (e.g. TypeError) with the Dart exception's toString().
+    if (typeof stack == 'string') {
+      try {  // toString is in a try-catch due to Issue 470.

[Jennifer Messerly, 2011/11/29 00:46:18]

Issue 470 is fixed--can you see if the try-catch can be removed?

+        var message = dartEx.toString();
+        if (/^(Type|Range)Error:/.test(stack)) {
+          // Remove JS message.
+          stack = stack.substring(stack.indexOf('\n') + 1);
+        }
+        stack = message + '\n' + stack;
+      } catch(_) {
+        stack = '' + dartEx.constructor.name + ': (corrupt)\n' + stack;
+      }
+    }
+    dartEx.stack = stack;
+    return dartEx;
+  }
+
   if (e instanceof TypeError) {
     switch(e.type) {
       case 'property_not_function':
       case 'called_non_callable':
         if (e.arguments[0] == null) {
-          res = new NullPointerException();
+          return attachStack(new NullPointerException());
         } else {
-          res = new ObjectNotClosureException();
+          return attachStack(new ObjectNotClosureException());
         }
         break;
       case 'non_object_property_call':
       case 'non_object_property_load':
-        res = new NullPointerException();
+        return attachStack(new NullPointerException());
         break;
       case 'undefined_method':
         if (e.arguments[0] == 'call' || e.arguments[0] == 'apply') {
-          res = new ObjectNotClosureException();
+          return attachStack(new ObjectNotClosureException());
         } else {
           // TODO(jmesserly): can this ever happen?
-          res = new NoSuchMethodException('', e.arguments[0], []);
+          // sra: Yes.

[Jennifer Messerly, 2011/11/29 00:46:18]

Can you add context about what conditions it happens? e.g.
// This happens with operators that aren't found because noSuchMethod fallbacks
are not correctly generated

(I think that's the only condition this should happen, but maybe you hit a
different one)

+          return attachStack(new NoSuchMethodException('', e.arguments[0], []));
         }
         break;
     }
   } else if (e instanceof RangeError) {
     if (e.message.indexOf('call stack') >= 0) {
-      res = new StackOverflowException();
+      return attachStack(new StackOverflowException());
     }
   }
-  if (res) {
-    // TODO(jmesserly): setting the stack property is not a long term solution.
-    // Also it causes the exception to print as if it were a JS TypeError or
-    // RangeError, instead of using the proper toString.
-    res.stack = e.stack;
-  }
-  return res;
+  return e;
 }""");
     }