Add terminal support checking. Fixes #41587

[keringar]

No description provided.

[rust-highfive]

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[Mark-Simulacrum]

Thanks for the PR!

Looks like you have some errors in the code. I'm personally not familiar with this area, so I don't know if that method exists, but it seems at least possible that it doesn't -- grepping for it in Rust's source returned nothing for me. Where did you expect the supports_reset method to come from?

[00:02:35] error: no method named `supports_reset` found for type `&mut std::boxed::Box<term::Terminal<Output=std::io::Stderr> + std::marker::Send + 'static>` in the current scope
[00:02:35]     --> /checkout/src/librustc_errors/emitter.rs:1379:22
[00:02:35]      |
[00:02:35] 1379 |                 if t.supports_reset() {
[00:02:35]      |                      ^^^^^^^^^^^^^^
[00:02:35] 
[00:02:35] error: no method named `supports_reset` found for type `&mut std::boxed::Box<term::Terminal<Output=emitter::BufferedWriter> + std::marker::Send + 'static>` in the current scope
[00:02:35]     --> /checkout/src/librustc_errors/emitter.rs:1384:22
[00:02:35]      |
[00:02:35] 1384 |                 if t.supports_reset() {
[00:02:35]      |                      ^^^^^^^^^^^^^^
[00:02:35] 
[00:02:35] error: aborting due to 2 previous errors

[keringar]

The supports_reset is supposed to be a method provided by the term::Terminal trait. https://stebalien.github.io/doc/term/term/trait.Terminal.html#tymethod.supports_reset. I assumed that the term crate in rust was provided by that term crate, but I guess it's its own in-tree version?

[Mark-Simulacrum]

Yeah, the compiler's term crate is in-tree (src/libterm). I'm not sure what current policy is on moving away from these in-tree crates to out of tree equivalents is (cc @alexcrichton).

We'll try to get you a decision on what to do here soon.

[keringar]

Thank you

[hanna-kruppe]

I asked @alexcrichton a while ago about libterm and he said it would be good to move to the crates.io version, he just hasn't found the time to do it yet. A PR doing that would be welcome (but ideally we'd fix #27812 first).

[alexcrichton]

Yes I'd love to see libterm from crates.io integrated into the compiler!

[keringar]

I can start moving rustc away from depending on an in-tree term. I'm assuming that it won't be affected by #27812 (cc @eddyb)