SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
casting a value to a u32 when it's originally an int, and it's exposed as int to users,
could end up in cases where a negative number would result as a positive one.
This doesn't really affect the value range of the attachment enum,
still I think the code was wrong.
Heavily tested.