[breaking batch] don't glob-export syntax::abi enums

[oli-obk]

r? @Manishearth

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @Manishearth (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[Manishearth]

While we're at it, should we also un-batch export TyFoo and ExprBar and friends from AST/HIR?

[Manishearth]

cc @erickt heads up

[oli-obk]

I'm creating a bunch of these PRs, then you can roll them up. Feels free to open an issue with checkboxes of things that should be done, in an order that your prefer.

[Manishearth]

Nah, this works

[Manishearth]

r+ on this one

[bluss]

Should it have the ususal [breaking-change] marker in the commit log or PR message? That's the usual marker.

[Manishearth]

the [breaking-batch] is for batching up breaking libsyntax changes

[bluss]

Is this a breaking change in the usual sense of [breaking-change]? Then it should have that tag.

[Manishearth]

Well, breaking libsyntax. Not sure if that qualifies as breaking; since many compiler changes break internals and we don't mark that as breaking either.

[oli-obk]

I'll mark it. Abi can show up in compiler plugins

[oli-obk]

merged into #31487