rustup which doesn't accept + arguments

[nikomatsakis]

I often want to find out "what is the real command that is running" so that I can (e.g.) launch rustc within gdb or something. I usually invoke rustc with something like:

rustc +rust-1-stage1 ~/tmp/issue-47206.rs -Ztreat-err-as-bug

It's annoying to me that I can't just add rustup which in front of that and have it emit something like:

/path/to/rust-1-stage1/rustc ~/tmp/issue-47206.rs -Ztreat-err-as-bug

Maybe something like rustup elaborate?

At minimum, I wish I could do rustup which +rust-1-stage1 or something.

[kinnison]

Assuming you'd be okay with rustup +rust-1-stage1 which rustc which is effectively what #1498 is proposing, then I suggest we add --toolchain support to rustup which and then have #1498 provide the +foo variant. Does that sound acceptable?

[BeniCheni]

then I suggest we add --toolchain support to rustup which ...

Hi, @kinnison, friendly note that I've given it a shot to add --toolchain option to rustup which in #2030.

and then have #1498 provide the +foo variant.

I'm interested in trying out. Can you give more hint what adding +foo variant implies? Does it mean rustup +custom-1 which rustc would work the same as rustup --toolchain=custom-1 which rustc?

[kinnison]

@BeniCheni Yes, the idea is that rustup +nightly which rustc would be the same as rustup which rustc --nightly and so on. So that it's the same as cargo +nightly run or rustfmt +nightly etc.