GCC plugin, detect 'typedef' and 'using'

I'm writing a GCC plugin and would like to identify typedef and using.

plugin.cpp

#include <gcc-plugin.h>#include <tree.h>#include <tree-pretty-print.h>#include <plugin-version.h>#include <c-family/c-common.h>#include <iostream>int plugin_is_GPL_compatible;static const std::string tree_code_str(enum tree_code code){    std::string str {get_tree_code_name(code)};    str += " (" + std::to_string(code) +")";    return str;}static const char* get_tree_name(tree t) {    if (t == NULL_TREE) {        return "<null>";    }    const char *name = get_name(t);    if (name) {        return name;    }    return "<no name>";}static const char* get_type_name_str(tree var_type){    const char *type_name = NULL;    if (TYPE_NAME(var_type) != NULL_TREE) {        tree type_name_tree = TYPE_NAME(var_type);        if (TREE_CODE(type_name_tree) == TYPE_DECL) {            type_name = IDENTIFIER_POINTER(DECL_NAME(type_name_tree));        } else if (TREE_CODE(type_name_tree) == IDENTIFIER_NODE) {            type_name = IDENTIFIER_POINTER(type_name_tree);        }    }    if (type_name) {        return type_name;    } else {        return "<no type name>";    }}static void plugin_finish_decl(void *gcc_data, void *user_data) {    tree decl = (tree) gcc_data;    std::cout << "TREE_CODE=[" << tree_code_str(TREE_CODE(decl)) << "] "<< "TREE_TYPE=[" << get_type_name_str(TREE_TYPE(decl)) << "] "<< "TREE_CODE(TREE_TYPE)=[" << tree_code_str(TREE_CODE(TREE_TYPE(decl))) << "] "<< "TREE_CODE(TYPE_NAME)=[" << tree_code_str(TREE_CODE(TYPE_NAME(decl))) << "] "<< "name=[" << get_tree_name(decl) << "] "<< std::endl;}int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version) {    if (!plugin_default_version_check(version, &gcc_version)) {        fprintf(stderr, "Incompatible GCC version\n");        return 1;    }    register_callback(plugin_info->base_name, PLUGIN_FINISH_DECL, plugin_finish_decl, NULL);    return 0;}

test.cpp

typedef int MyInt;MyInt var {};int main() { return 0; }

output

TREE_CODE=[var_decl (36)] TREE_TYPE=[MyInt] TREE_CODE(TREE_TYPE)=[integer_type (8)] TREE_CODE(TYPE_NAME)=[identifier_node (1)] name=[var]

As we can see from the output, MyInt is of type integer and notTYPE_DECL. GCC Documentation

I tried with GCC version 10 and 13. The result is the same.

Do you have an explanation? The GCC documentation doesn't seem clear on this point?