https://stackoverflow.com/questions/29971097/how-to-create-ast-with-antlr4 這個很值得仔細看
https://github.com/alongubkin/modern/tree/master/compiler/ModernCompiler
https://www.jianshu.com/p/4bedad8dd70a
https://www.ibm.com/developerworks/cn/java/j-lo-antlr/index.html