[New custom build] Implement platform-specific dependencies

[tomaka]

cc #610

[alexcrichton]

This is actually called pretty frequently due to the recursive nature of resolve, and I think this could get away with the more cheap Option<&'a str>, would that be possible?

[alexcrichton]

Looks fantastic, thanks so much @tomaka! As mentioned on IRC I think I'll wait to merge this until the RFC gets merged, but hopefully that won't take too long!

[tomaka]

Updated

[tomaka]

Oops, I forgot to remove the call to rustc_version in cargo_rustc::Context

[tomaka]

Updated

[alexcrichton]

It's probably ok to omit the ref + clone() here (as well as below)

[alexcrichton]

Looks fantastic, thanks @tomaka! I'll hold off on this pending the resolution of rust-lang/rfcs#403.

[alexcrichton]

BTW: I added a location in which we'll need to upload this information to the registry, you'll just need to fill it out: https://github.com/rust-lang/cargo/blob/master/src/cargo/ops/registry.rs#L75

[tomaka]

BTW: I added a location in which we'll need to upload this information to the registry, you'll just need to fill it out: https://github.com/rust-lang/cargo/blob/master/src/cargo/ops/registry.rs#L75

Done

[alexcrichton]

Ah I knew I forgot one other location! https://github.com/rust-lang/cargo/blob/master/src/cargo/sources/registry.rs#L420 (I can fix this up after merging as well, which can hopefully happen today!)

[tomaka]

I fixed it too

[alexcrichton]

Thanks @tomaka!

[alexcrichton]

RFC was approved this afternoon, let's see what bors thinks of this!