Hash#replace

static VALUE
rb_hash_replace(VALUE hash, VALUE hash2)
{
    rb_hash_modify_check(hash);
    if (hash == hash2) return hash;
    if (hash_iterating_p(hash)) {
        rb_raise(rb_eRuntimeError, "can't replace hash during iteration");
    }
    hash2 = to_hash(hash2);

    COPY_DEFAULT(hash, hash2);

    if (RHASH_AR_TABLE_P(hash)) {
        hash_ar_free_and_clear_table(hash);
    }
    else {
        hash_st_free_and_clear_table(hash);
    }

    hash_copy(hash, hash2);

    return hash;
}