rustc-dev-guide Document inert vs active attributes

This PR adds a subsection to the 'Syntax and AST' section describing inert vs active attributes.

For consistency, I've also updated the '#[test] implementation' page to stop referring to `#[test]' as a 'built in' attribute, since that has a specific meaning defined on this page.

Apr 16 '21 21:04 Aaron1011

cfg and cfg_attr are probably worth mentioning as third category because they are both built-in (in the sense that they don't go through name resolution) and active (expanded directly by the compiler).

Apr 17 '21 06:04 petrochenkov

@Aaron1011 will you be able to work on this to get it over the finish line? I'd love to see it merged.

Jul 04 '21 18:07 rylev

@Aaron1011 I'm not sure if this is still up-to-date, could you check? It'd also be great if you could address review comments.

Nov 20 '22 04:11 JohnTitor

I'm not sure what's the current status of this PR, but I guess it may be better to merge it and continue working on it on master. Opinions?.

Feb 15 '23 14:02 spastorino

I'm not sure what's the current status of this PR, but I guess it may be better to merge it and continue working on it on master. Opinions?.

Any comment about this :point_up: ?

Oct 26 '23 14:10 spastorino