diff --git a/modules/change_detection/src/parser/ast.js b/modules/change_detection/src/parser/ast.js
index e38011b3eb..042630242c 100644
--- a/modules/change_detection/src/parser/ast.js
+++ b/modules/change_detection/src/parser/ast.js
@@ -1,5 +1,5 @@
 import {FIELD, autoConvertAdd, isBlank, isPresent, FunctionWrapper, BaseException} from "facade/lang";
-import {List, Map, ListWrapper, MapWrapper} from "facade/collection";
+import {List, Map, ListWrapper, StringMapWrapper} from "facade/collection";
 import {ContextWithVariableBindings} from "./context_with_variable_bindings";
 
 export class AST {
@@ -162,14 +162,7 @@ export class KeyedAccess extends AST {
   eval(context) {
     var obj = this.obj.eval(context);
     var key = this.key.eval(context);
-
-    if (obj instanceof Map) {
-      return MapWrapper.get(obj, key);
-    } else if (obj instanceof List) {
-      return ListWrapper.get(obj, key);
-    } else {
-      return obj[key];
-    }
+    return obj[key];
   }
 
   get isAssignable() {
@@ -179,14 +172,7 @@ export class KeyedAccess extends AST {
   assign(context, value) {
     var obj = this.obj.eval(context);
     var key = this.key.eval(context);
-
-    if (obj instanceof Map) {
-      MapWrapper.set(obj, key, value);
-    } else if (obj instanceof List) {
-      ListWrapper.set(obj, key, value);
-    } else {
-      obj[key] = value;
-    }
+    obj[key] = value;
     return value;
   }
 
@@ -251,9 +237,9 @@ export class LiteralMap extends AST {
   }
 
   eval(context) {
-    var res = MapWrapper.create();
+    var res = StringMapWrapper.create();
     for(var i = 0; i < this.keys.length; ++i) {
-      MapWrapper.set(res, this.keys[i], this.values[i].eval(context));
+      StringMapWrapper.set(res, this.keys[i], this.values[i].eval(context));
     }
     return res;
   }
@@ -281,13 +267,8 @@ export class Binary extends AST {
     }
     var right = this.right.eval(context);
 
-    // Null check for the operations.
-    if (isBlank(left)|| isBlank(right)) {
-      throw new BaseException("One of the operands is not defined");
-    }
-
     switch (this.operation) {
-      case '+'  : return autoConvertAdd(left, right);
+      case '+'  : return left + right;
       case '-'  : return left - right;
       case '*'  : return left * right;
       case '/'  : return left / right;
diff --git a/modules/change_detection/src/record_range.js b/modules/change_detection/src/record_range.js
index f35ef83f5b..d6b579b764 100644
--- a/modules/change_detection/src/record_range.js
+++ b/modules/change_detection/src/record_range.js
@@ -13,7 +13,7 @@ import {
 
 import {FIELD, IMPLEMENTS, isBlank, isPresent, int, toBool, autoConvertAdd, BaseException,
   NumberWrapper} from 'facade/lang';
-import {List, Map, ListWrapper, MapWrapper} from 'facade/collection';
+import {List, Map, ListWrapper, MapWrapper, StringMapWrapper} from 'facade/collection';
 import {ContextWithVariableBindings} from './parser/context_with_variable_bindings';
 import {
   AccessMember,
@@ -524,9 +524,9 @@ function _arrayFn(length:int) {
 
 function _mapFn(keys:List, length:int) {
   function buildMap(values) {
-    var res = MapWrapper.create();
+    var res = StringMapWrapper.create();
     for(var i = 0; i < keys.length; ++i) {
-      MapWrapper.set(res, keys[i], values[i]);
+      StringMapWrapper.set(res, keys[i], values[i]);
     }
     return res;
   }
@@ -554,6 +554,5 @@ function _mapGetter(key) {
 }
 
 function _keyedAccess(obj, args) {
-  var key = args[0];
-  return obj instanceof Map ? MapWrapper.get(obj, key):obj[key];
+  return obj[args[0]];
 }
diff --git a/modules/change_detection/test/change_detector_spec.js b/modules/change_detection/test/change_detector_spec.js
index d063e1581a..882292723d 100644
--- a/modules/change_detection/test/change_detector_spec.js
+++ b/modules/change_detection/test/change_detector_spec.js
@@ -118,11 +118,11 @@ export function main() {
       it("should support literal maps", () => {
         var c = createChangeDetector('map', '{z:1}');
         c["changeDetector"].detectChanges();
-        expect(MapWrapper.get(c["dispatcher"].loggedValues[0][0], 'z')).toEqual(1);
+        expect(c["dispatcher"].loggedValues[0][0]['z']).toEqual(1);
 
         c = createChangeDetector('map', '{z:a}', new TestData(1));
         c["changeDetector"].detectChanges();
-        expect(MapWrapper.get(c["dispatcher"].loggedValues[0][0], 'z')).toEqual(1);
+        expect(c["dispatcher"].loggedValues[0][0]['z']).toEqual(1);
       });
 
       it("should support binary operations", () => {
diff --git a/modules/change_detection/test/parser/parser_spec.js b/modules/change_detection/test/parser/parser_spec.js
index d0f907249e..0c32e5075b 100644
--- a/modules/change_detection/test/parser/parser_spec.js
+++ b/modules/change_detection/test/parser/parser_spec.js
@@ -134,25 +134,6 @@ export function main() {
           expectEval("(1+2)*3").toEqual((1+2)*3);
         });
 
-        it('should auto convert ints to strings', () => {
-          expectEval("'str ' + 4").toEqual("str 4");
-          expectEval("4 + ' str'").toEqual("4 str");
-          expectEval("4 + 4").toEqual(8);
-          expectEval("4 + 4 + ' str'").toEqual("8 str");
-          expectEval("'str ' + 4 + 4").toEqual("str 44");
-        });
-
-        it('should throw when one of the operands is null', () => {
-          expectEvalError("null < 0").toThrowError();
-          expectEvalError("null * 3").toThrowError();
-          expectEvalError("null + 6").toThrowError();
-          expectEvalError("5 + null").toThrowError();
-          expectEvalError("null - 4").toThrowError();
-          expectEvalError("3 - null").toThrowError();
-          expectEvalError("null + null").toThrowError();
-          expectEvalError("null - null").toThrowError();
-        });
-
         it('should parse an empty string', () => {
           expectEval('').toBeNull();
         });
@@ -168,7 +149,7 @@ export function main() {
         });
 
         it('should evaluate map', () => {
-          expectEval("{}").toEqual(MapWrapper.create());
+          expectEval("{}").toEqual({});
           expectEval("{a:'b'}['a']").toEqual('b');
           expectEval("{'a':'b'}['a']").toEqual('b');
           expectEval("{\"a\":'b'}['a']").toEqual('b');
@@ -285,15 +266,15 @@ export function main() {
         });
 
         it("should support map updates", () => {
-          var context = td(MapWrapper.createFromPairs([["key", 100]]));
+          var context = td({"key" : 100});
           expectEval('a["key"] = 200', context).toEqual(200);
-          expect(MapWrapper.get(context.a, "key")).toEqual(200);
+          expect(context.a["key"]).toEqual(200);
         });
 
         it("should support array/map updates", () => {
-          var context = td([MapWrapper.createFromPairs([["key", 100]])]);
+          var context = td([{"key" : 100}]);
           expectEval('a[0]["key"] = 200', context).toEqual(200);
-          expect(MapWrapper.get(context.a[0], "key")).toEqual(200);
+          expect(context.a[0]["key"]).toEqual(200);
         });
 
         it('should allow assignment after array dereference', () => {
diff --git a/modules/facade/src/lang.dart b/modules/facade/src/lang.dart
index bc9e857cd7..0cbcaba349 100644
--- a/modules/facade/src/lang.dart
+++ b/modules/facade/src/lang.dart
@@ -33,21 +33,6 @@ bool toBool(x) {
   return false;
 }
 
-autoConvertAdd(a, b) {
-  if (a != null && b != null) {
-    if (a is String && b is! String) {
-      return a + b.toString();
-    }
-    if (a is! String && b is String) {
-      return a.toString() + b;
-    }
-    return a + b;
-  }
-  if (a != null) return a;
-  if (b != null) return b;
-  return 0;
-}
-
 String stringify(obj) => obj.toString();
 
 class StringWrapper {
diff --git a/modules/facade/src/lang.es6 b/modules/facade/src/lang.es6
index 70606e88cd..30fb0d4e57 100644
--- a/modules/facade/src/lang.es6
+++ b/modules/facade/src/lang.es6
@@ -30,10 +30,6 @@ export function toBool(obj) {
   return !!obj;
 }
 
-export function autoConvertAdd(a, b) {
-  return a + b;
-}
-
 export function stringify(token):string {
   if (typeof token === 'string') {
     return token;