I don't know if any API does this, but I often wished that APIs I used could mark up just a tiny, tiny subset as @FutureSafe, like the opposite of tagging deprecated code, so that for smaller projects you could stick to only or mostly those parts and know that you can come back after 2 years or 20 years and things still work. Maybe throw in a compiler flag to verify that nothing not-@FutureSafe is used by accident. Sometimes you just want to write something small, once, and not have to actively maintain it forever. Outside of shell-scripts or retro-platform code you can barely write Hello World for any target today and feel confident that it will still run six months from now.