crate version number

[jesse99]

There should be a reasonably simple way to get at the version number and related meta-data from within a crate, e.g. to better support a --version command line argument.

[graydon]

nominating for feature complete

[brson]

cc #6322 which talks about making crate map available at runtime

[graydon]

just a bug, removing milestone/nomination.

[graydon]

Visiting for triage. Looks like we currently do this:

$ ./x86_64-unknown-linux-gnu/stage1/bin/rustc --ls ./x86_64-unknown-linux-gnu/stage0/lib/librustc-d3cb8c2ccd84a7a7-0.8-pre.so 
=Crate Attributes (d3cb8c2ccd84a7a7)=
#[link(name = "rustc",
       vers = "0.8-pre",
       uuid = "0ce89b41-2f92-459e-bbc1-8f5fe32f16cf",
       url = "https://github.com/mozilla/rust/tree/master/src/rustc")]
#[comment = "The Rust compiler"]
#[license = "MIT/ASL2"]
#[crate_type = "lib"]


=External Dependencies=
1 std-6c65cf4b443341b1-0.8-pre
2 extra-a7c050cfd46b2c9a-0.8-pre
3 syntax-64629f7f0c6a9bc-0.8-pre

Is this sufficient?

[huonw]

We no longer have #[link] (replaced by #[crate_id]), and we support --crate-id to retrieve this from source, but not from the compiled crates. Having it support both would be neat.

[steveklabnik]

I think cargo effectively fixes this issue.

[alexcrichton]

Yes, #[crate_name] means that rustc no longer understands anything about versions.