A class/module name is now defined for meta programing

src/variable.c

@@ -344,6 +344,8 @@ mrb_iv_get(mrb_state *mrb, mrb_value obj, mrb_sym sym)
   return mrb_nil_value();
 }
 
+static inline void assign_class_name(mrb_state *mrb, struct RObject *obj, mrb_sym sym, mrb_value v);
+
 MRB_API void
 mrb_obj_iv_set(mrb_state *mrb, struct RObject *obj, mrb_sym sym, mrb_value v)
 {
@@ -352,6 +354,7 @@ mrb_obj_iv_set(mrb_state *mrb, struct RObject *obj, mrb_sym sym, mrb_value v)
   if (MRB_FROZEN_P(obj)) {
     mrb_raisef(mrb, E_FROZEN_ERROR, "can't modify frozen %S", mrb_obj_value(obj));
   }
+  assign_class_name(mrb, obj, sym, v);
   if (!obj->iv) {
     obj->iv = iv_new(mrb);
   }
@@ -360,6 +363,36 @@ mrb_obj_iv_set(mrb_state *mrb, struct RObject *obj, mrb_sym sym, mrb_value v)
   mrb_write_barrier(mrb, (struct RBasic*)obj);
 }
 
+static inline mrb_bool
+is_namespace(enum mrb_vtype tt)
+{
+  return tt == MRB_TT_CLASS || tt == MRB_TT_MODULE ? TRUE : FALSE;
+}
+
+static inline void
+assign_class_name(mrb_state *mrb, struct RObject *obj, mrb_sym sym, mrb_value v)
+{
+  if (is_namespace(obj->tt) && is_namespace(mrb_type(v)) && ISUPPER(mrb_sym2name(mrb, sym)[0])) {
+    struct RObject *c = mrb_obj_ptr(v);
+    mrb_sym id_classname = mrb_intern_lit(mrb, "__classname__");
+    mrb_value o = mrb_obj_iv_get(mrb, c, id_classname);
+
+    if (mrb_nil_p(o)) {
+      mrb_sym id_outer = mrb_intern_lit(mrb, "__outer__");
+      o = mrb_obj_iv_get(mrb, c, id_outer);
+
+      if (mrb_nil_p(o)) {
+        if ((struct RClass *)obj == mrb->object_class) {
+          mrb_obj_iv_set(mrb, c, id_classname, mrb_symbol_value(sym));
+        }
+        else {
+          mrb_obj_iv_set(mrb, c, id_outer, mrb_obj_value(obj));
+        }
+      }
+    }
+  }
+}
+
 MRB_API void
 mrb_iv_set(mrb_state *mrb, mrb_value obj, mrb_sym sym, mrb_value v)
 {