Implement "VisitAssignment" method

[yll690]

I don't know why did VisitAssignment(ResolveResult lhs, ResolveResult rhs) simply throw an excption. I add some code to it, and it looks working well. If there are some reasons or problems please tell me.😋

I certify that I own, and have sufficient rights to contribute, all source code and related material intended to be compiled or integrated with the source code for the #develop open source product (the "Contribution"). My Contribution is licensed under the MIT License.