ObjectSpace::WeakKeyMap#[]=

static VALUE
wkmap_aset(VALUE self, VALUE key, VALUE val)
{
    struct weakkeymap *w;
    TypedData_Get_Struct(self, struct weakkeymap, &weakkeymap_type, w);

    if (!FL_ABLE(key) || SYMBOL_P(key) || RB_BIGNUM_TYPE_P(key) || RB_TYPE_P(key, T_FLOAT)) {
        rb_raise(rb_eArgError, "WeakKeyMap keys must be garbage collectable");
        UNREACHABLE_RETURN(Qnil);
    }

    struct wkmap_aset_args args = {
        .new_key = key,
        .new_val = val,
    };

    st_update(w->table, (st_data_t)&key, wkmap_aset_replace, (st_data_t)&args);

    RB_OBJ_WRITTEN(self, Qundef, key);
    RB_OBJ_WRITTEN(self, Qundef, val);

    return val;
}