Fix class name validation in `Struct.new`

Before this patch:

  $ bin/mruby -e 'p Struct.new("A-")'
  #=> Struct::"A-"

After this patch:

  $ bin/mruby -e 'p Struct.new("A-")'
  #=> NameError: identifier A- needs to be constant

include/mruby/class.h

@@ -88,6 +88,7 @@ MRB_API struct RClass* mrb_class_real(struct RClass* cl);
 mrb_value mrb_instance_new(mrb_state *mrb, mrb_value cv);
 
 void mrb_class_name_class(mrb_state*, struct RClass*, struct RClass*, mrb_sym);
+mrb_bool mrb_const_name_p(mrb_state*, const char*, mrb_int);
 mrb_value mrb_class_find_path(mrb_state*, struct RClass*);
 void mrb_gc_mark_mt(mrb_state*, struct RClass*);
 size_t mrb_gc_mark_mt_size(mrb_state*, struct RClass*);

mrbgems/mruby-struct/src/struct.c

@@ -212,7 +212,7 @@ make_struct(mrb_state *mrb, mrb_value name, mrb_value members, struct RClass *kl
     /* old style: should we warn? */
     mrb_to_str(mrb, name);
     id = mrb_obj_to_sym(mrb, name);
-    if (!is_const_id(mrb, mrb_sym2name_len(mrb, id, NULL))) {
+    if (!mrb_const_name_p(mrb, RSTRING_PTR(name), RSTRING_LEN(name))) {
       mrb_name_error(mrb, id, "identifier %S needs to be constant", name);
     }
     if (mrb_const_defined_at(mrb, mrb_obj_value(klass), id)) {

mrbgems/mruby-struct/test/struct.rb

@@ -181,6 +181,10 @@ assert("Struct.new does not allow array") do
   end
 end
 
+assert("Struct.new does not allow invalid class name") do
+  assert_raise(NameError) { Struct.new("Test-", :a) }
+end
+
 assert("Struct.new generates subclass of Struct") do
   begin
     original_struct = Struct

src/class.c

@@ -77,6 +77,12 @@ mrb_class_name_class(mrb_state *mrb, struct RClass *outer, struct RClass *c, mrb
   mrb_obj_iv_set_force(mrb, (struct RObject*)c, nsym, name);
 }
 
+mrb_bool
+mrb_const_name_p(mrb_state *mrb, const char *name, mrb_int len)
+{
+  return len > 0 && ISUPPER(name[0]) && mrb_ident_p(name+1, len-1);
+}
+
 static void
 setup_class(mrb_state *mrb, struct RClass *outer, struct RClass *c, mrb_sym id)
 {
@@ -1852,18 +1858,12 @@ mrb_mod_undef(mrb_state *mrb, mrb_value mod)
   return mrb_nil_value();
 }
 
-static mrb_bool
-const_name_p(mrb_state *mrb, const char *name, mrb_int len)
-{
-  return len > 0 && ISUPPER(name[0]) && mrb_ident_p(name+1, len-1);
-}
-
 static void
 check_const_name_sym(mrb_state *mrb, mrb_sym id)
 {
   mrb_int len;
   const char *name = mrb_sym2name_len(mrb, id, &len);
-  if (!const_name_p(mrb, name, len)) {
+  if (!mrb_const_name_p(mrb, name, len)) {
     mrb_name_error(mrb, id, "wrong constant name %S", mrb_sym2str(mrb, id));
   }
 }