fix($parse): correctly assign expressions who's path is undefined and that use brackets notation

Closes angular#8039

Author: rodyhaddad

src/ng/parse.js

@@ -683,7 +683,9 @@ Parser.prototype = {
       return getter(self || object(scope, locals));
     }, {
       assign: function(scope, value, locals) {
-        return setter(object(scope, locals), field, value, parser.text);
+        var o = object(scope, locals);
+        if (!o) object.assign(scope, o = {});
+        return setter(o, field, value, parser.text);
       }
     });
   },
@@ -708,6 +710,7 @@ Parser.prototype = {
         var key = indexFn(self, locals);
         // prevent overwriting of Function.constructor which would break ensureSafeObject check
         var safe = ensureSafeObject(obj(self, locals), parser.text);
+        if (!safe) obj.assign(self, safe = {});
         return safe[key] = value;
       }
     });

test/ng/parseSpec.js

@@ -1077,6 +1077,22 @@ describe('parser', function() {
           fn.assign(scope, 123);
           expect(scope).toEqual({a:123});
         }));
+
+        it('should expose working assignment function for expressions ending with brackets', inject(function($parse) {
+          var fn = $parse('a.b["c"]');
+          expect(fn.assign).toBeTruthy();
+          var scope = {};
+          fn.assign(scope, 123);
+          expect(scope.a.b.c).toEqual(123);
+        }));
+
+        it('should expose working assignment function for expressions with brackets in the middle', inject(function($parse) {
+          var fn = $parse('a["b"].c');
+          expect(fn.assign).toBeTruthy();
+          var scope = {};
+          fn.assign(scope, 123);
+          expect(scope.a.b.c).toEqual(123);
+        }));
       });