fix(parser): Makes the setter code more robust.

lib/parser.dart

@@ -216,22 +216,18 @@ setterChild(obj, childKey, value) {
 
   InstanceMirror instanceMirror = reflect(obj);
   Symbol curSym = new Symbol(childKey);
-  try {
-    // maybe it is a member field?
-    return instanceMirror.setField(curSym, value).reflectee;
-  } catch (e) {
-    throw "$e \n\n${e.stacktrace}";
-  }
+  // maybe it is a member field?
+  return instanceMirror.setField(curSym, value).reflectee;
 }
 
 setter(obj, path, setValue) {
   var element = path.split('.');
   for (var i = 0; element.length > 1; i++) {
     var key = element.removeAt(0);
-    var propertyObj = obj[key];
+    var propertyObj = getterChild(obj, key)[1];
     if (propertyObj == null) {
       propertyObj = {};
-      obj[key] = propertyObj;
+      setterChild(obj, key, propertyObj);
     }
     obj = propertyObj;
   }
@@ -494,7 +490,8 @@ class Parser {
           'at column ${t.index + 1} in';
       return 'Parser Error: $s $location [$text]';
     }
-    evalError(String s) => 'Eval Error: $s while evaling [$text]';
+    evalError(String s, [stack]) => 'Eval Error: $s while evaling [$text]' +
+        (stack != null ? '\n\nFROM:\n$stack' : '');
 
     Token peekToken() {
       if (tokens.length == 0)
@@ -680,8 +677,13 @@ class Parser {
           throw parserError('Expression ${tokensText(ts)} is not assignable', token);
         }
         right = logicalOR();
-        return new ParsedFn((scope, locals) =>
-          left.assign(scope, right(scope, locals), locals));
+        return new ParsedFn((scope, locals) {
+          try {
+            return left.assign(scope, right(scope, locals), locals);
+          } catch (e, s) {
+            throw evalError('Caught $e', s);
+          }
+        });
       } else {
         return left;
       }

test/parser_spec.dart

@@ -428,6 +428,82 @@ main() {
       });
     });
 
+    describe('setters', () {
+      it('should set a field in a map', () {
+        scope['map'] = {};
+        eval('map["square"] = 6');
+        eval('map.dot = 7');
+
+        expect(scope['map']['square']).toEqual(6);
+        expect(scope['map']['dot']).toEqual(7);
+      });
+
+
+      it('should set a field in a list', () {
+        scope['list'] = [];
+        eval('list[3] = 2');
+
+        expect(scope['list'].length).toEqual(4);
+        expect(scope['list'][3]).toEqual(2);
+      });
+
+
+      it('should set a field on an object', () {
+        scope['obj'] = new SetterObject();
+        eval('obj.field = 1');
+
+        expect(scope['obj'].field).toEqual(1);
+      });
+
+
+      it('should set a setter on an object', () {
+        scope['obj'] = new SetterObject();
+        eval('obj.setter = 2');
+
+        expect(scope['obj'].setterValue).toEqual(2);
+      });
+
+
+      it('should set a []= on an object', () {
+        scope['obj'] = new OverloadObject();
+        eval('obj.overload = 7');
+
+        expect(scope['obj'].overloadValue).toEqual(7);
+      });
+
+
+      it('should set a field in a nested map on an object', () {
+        scope['obj'] = new SetterObject();
+        eval('obj.map.mapKey = 3');
+
+        expect(scope['obj'].map['mapKey']).toEqual(3);
+      });
+
+
+      it('should set a field in a nested object on an object', () {
+        scope['obj'] = new SetterObject();
+        eval('obj.nested.field = 1');
+
+        expect(scope['obj'].nested.field).toEqual(1);
+      });
+
+
+      it('should create a map for dotted acces', () {
+        scope['obj'] = new SetterObject();
+        eval('obj.field.key = 4');
+
+        expect(scope['obj'].field['key']).toEqual(4);
+      });
+
+
+      it('should throw a nice error for type mismatch', () {
+        scope['obj'] = new SetterObject();
+        expect(() {
+          eval('obj.integer = "hello"');
+        }).toThrow("Eval Error: Caught type 'String' is not a subtype of type 'int' of 'value'. while evaling [obj.integer = \"hello\"]");
+      });
+    });
+
     describe('test cases imported from AngularJS', () {
       //// ==== IMPORTED ITs
       it('should parse expressions', () {
@@ -809,6 +885,25 @@ main() {
   });
 }
 
+class SetterObject {
+  var field;
+  int integer;
+  var map = {};
+
+  var nest;
+  SetterObject get nested => nest != null ? nest : (nest = new SetterObject());
+
+  var setterValue;
+  void set setter(x) { setterValue = x; }
+}
+
+class OverloadObject {
+  var overloadValue;
+  operator []=(String name, var value) {
+    overloadValue = value;
+  }
+}
+
 class ScopeWithErrors {
   String get boo { dump("got a boo"); throw "boo to you"; }
   String foo() { dump("got a foo"); throw "foo to you"; }