rustc is using three versions of rand

[scottmcm]

I noticed this scrolling by while "Building stage0 compiler artifacts" today:

   Compiling rand_pcg v0.1.1
   Compiling rand v0.6.1
   Compiling flate2 v1.0.6
   Compiling rand v0.4.3
   Compiling rand v0.5.5
   Compiling winapi-util v0.1.1

Optimistically flagging E-easy

[JohnTitor]

@scottmcm I'd like to work on this, how can I fix? make rustc use one version(maybe v0.6.1)?

[ishitatsuyuki]

@JohnTitor You will need to look into each dependency that depends on rand (by searching through Cargo.lock), check if they have a newer version that depends on new rand, and finally use cargo update -p <crate> to upgrade those crates.

[JohnTitor]

@ishitatsuyuki Thanks! When I checked, it seems each rand version is used.

[ishitatsuyuki]

Yeah, it's natural that they are all used, and you could try to eliminate those crates using old rand by upgrading or refactoring. That said, there isn't much drawback with an older rand, so in that case this issue can be just closed.

[JohnTitor]

Oh, I'm sorry, I misunderstood. Hmmm, I think we don't have to fix this quickly and this may be a catalyst for a newbie like me to contribute, so I leave this, okay?

[hellow554]

@ishitatsuyuki but one could argue that it will lower the time to compile so it's worth to fix IMHO ;)

[JohnTitor]

Uh, would it be better to fix?

[hellow554]

Disclaimer: I'm not a core member, but IMHO this is worth fixing. Also scottmcm who is a core member opened this issue, so I guess you're good to go and fix that issue @JohnTitor :)

[JohnTitor]

Okay, I want to try to fix. For instance, crossbeam-channel depends on rand v0.5.5, how can I update or refactor this?

[hellow554]

That's one thing you can't edit, because rand is a dependency of crossbeam-channel here, so the crate crossbeam-channel needs to update its dependecy (maybe it already did and you just need to update crossbeam-channel itself)?

[Aaron1011]

For future reference, running cargo tree -d from src/rustc is an easy way to identify the source of all duplicates.

[JohnTitor]

Thanks @Aaron1011 ! I got this tree(gist).
I updated parking_lot, but rustc-rayon v0.1.1 is latest and depends on rand v0.4.3(https://crates.io/crates/rustc-rayon).
What should I do?

[scottmcm]

@hellow554 I'm not on compiler (or core), so don't take my word on this one 🙂

@JohnTitor It looks like upstream rayon needs 0.5, so you could consider making a PR to upgrade it to 0.6. (Maybe ask someone on rayon first.) Also, it seems that rustc-rayon hasn't been updated in 6+ months, so they'd probably appreciate a PR to upgrade it to newer upstream.