Extract `RHASH_IDENTHASH_P`

hash.c

@@ -394,6 +394,8 @@ const struct st_hash_type rb_hashtype_ident = {
     rb_ident_hash,
 };
 
+#define RHASH_IDENTHASH_P(hash) (RHASH_TYPE(hash) == &identhash)
+
 typedef st_index_t st_hash_t;
 
 /*
@@ -2956,7 +2958,7 @@ rb_hash_aset(VALUE hash, VALUE key, VALUE val)
 
     rb_hash_modify(hash);
 
-    if (RHASH_TYPE(hash) == &identhash || rb_obj_class(key) != rb_cString) {
+    if (RHASH_IDENTHASH_P(hash) || rb_obj_class(key) != rb_cString) {
         RHASH_UPDATE_ITER(hash, iter_p, key, hash_aset, val);
     }
     else {
@@ -4162,7 +4164,7 @@ rb_hash_assoc(VALUE hash, VALUE key)
 
     if (RHASH_EMPTY_P(hash)) return Qnil;
 
-    if (RHASH_ST_TABLE_P(hash) && RHASH_ST_TABLE(hash)->type != &identhash) {
+    if (RHASH_ST_TABLE_P(hash) && !RHASH_IDENTHASH_P(hash)) {
         VALUE value = Qundef;
         st_table assoctable = *RHASH_ST_TABLE(hash);
         assoctable.type = &(struct st_hash_type){
@@ -4439,7 +4441,7 @@ rb_hash_compare_by_id(VALUE hash)
 VALUE
 rb_hash_compare_by_id_p(VALUE hash)
 {
-    return RBOOL(RHASH_ST_TABLE_P(hash) && RHASH_ST_TABLE(hash)->type == &identhash);
+    return RBOOL(RHASH_IDENTHASH_P(hash));
 }
 
 VALUE