eval.c:521
int
rb_method_boundp(klass, id, ex)
    VALUE klass;
    ID id;
    int ex;
{
    struct cache_entry *ent;
    int noex;

    /* is it in the method cache? */
    ent = cache + EXPR1(klass, id);
    if (ent->mid == id && ent->klass == klass) {
	if (ex && (ent->noex & NOEX_PRIVATE))
	    return Qfalse;
	if (!ent->method) return Qfalse;
	return Qtrue;
    }
    if (rb_get_method_body(&klass, &id, &noex)) {
	if (ex && (noex & NOEX_PRIVATE))
	    return Qfalse;
	return Qtrue;
    }
    return Qfalse;
}
