In file included from main.cpp:121:0:
format_visitor.h: In member function 'virtual void FormatVisitor::Visit(const MethodDeclarationNode*)':
format_visitor.h:75:19: error: 'const class MethodDeclarationNode' has no member named 'Arg'
         if (node->Arg().size()) {
                   ^~~
format_visitor.h:76:42: error: 'const class MethodDeclarationNode' has no member named 'Arg'
             for (size_t i = 0; i < node->Arg().size() - 1; ++i) {
                                          ^~~
format_visitor.h:77:35: error: 'const class MethodDeclarationNode' has no member named 'Arg'
                 this->Visit(node->Arg()[i]);
                                   ^~~
format_visitor.h:81:31: error: 'const class MethodDeclarationNode' has no member named 'Arg'
             this->Visit(node->Arg()[node->Arg().size() - 1]);
                               ^~~
format_visitor.h:81:43: error: 'const class MethodDeclarationNode' has no member named 'Arg'
             this->Visit(node->Arg()[node->Arg().size() - 1]);
                                           ^~~