multiple matching crates for rustc_serialize panic

[gibfahn]

Minimal repro:

#![feature(rustc_private)]
extern crate rustc_serialize;
use rustc_serialize::hex::ToHex;

fn main() {
    println!("Use toHex: {}", [0xFF_u8].to_hex());
}

• rustc: nightly-x86_64-apple-darwin - rustc 1.17.0-nightly (49c67bd63 2017-03-24)
• clippy v0.0.121

Error:

➜ cargo clippy
   Compiling clippy_panic v0.1.0 (file:///Users/gib/tmp/clippy_panic)
error[E0464]: multiple matching crates for `rustc_serialize`
 --> src/main.rs:2:1
  |
2 | extern crate rustc_serialize;
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: candidates:
  = note: path: /Users/gib/tmp/clippy_panic/target/debug/deps/librustc_serialize-54d2bf33b1d4b0b0.rlib
  = note: crate name: rustc_serialize
  = note: path: /Users/gib/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/lib/librustc_serialize-fde13340fc7641e7.rlib
  = note: crate name: rustc_serialize

error[E0463]: can't find crate for `rustc_serialize`
 --> src/main.rs:2:1
  |
2 | extern crate rustc_serialize;
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate

error: aborting due to 2 previous errors

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:455
note: Run with `RUST_BACKTRACE=1` for a backtrace.
thread 'main' panicked at 'rustc_thread failed: Any', src/libcore/result.rs:859
error: Could not compile `clippy_panic`.

To learn more, run the command again with --verbose.
  = note: path: /Users/gib/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/lib/librustc_serialize-fde13340fc7641e7.rlib
  = note: crate name: rustc_serialize

error[E0463]: can't find crate for `rustc_serialize`
 --> src/main.rs:3:1
  |
3 | extern crate rustc_serialize;
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate

error: aborting due to 2 previous errors

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:455
note: Run with `RUST_BACKTRACE=1` for a backtrace.
thread 'main' panicked at 'rustc_thread failed: Any', src/libcore/result.rs:859
error: Could not compile `five`.

To learn more, run the command again with --verbose.

[Manishearth]

You should delete the build directory.

[gibfahn]

Okay, that works for my (I guess too-minimal) test case, but not for the app I originally had the problem with, as that one also uses the crypto crate (looks like that depends on the external rustc-serialize).

Cargo.toml:

[dependencies]
rust-crypto = "^0.2"

Cargo.lock (relevant lines)

[[package]]
name = "rust-crypto"
version = "0.2.36"
source = "registry+https://github.com/rust-lang/crates.io-index"
dependencies = [
 "gcc 0.3.45 (registry+https://github.com/rust-lang/crates.io-index)",
 "libc 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
 "rand 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
 "rustc-serialize 0.3.23 (registry+https://github.com/rust-lang/crates.io-index)",
 "time 0.1.36 (registry+https://github.com/rust-lang/crates.io-index)",
]

[[package]]
name = "rustc-serialize"
version = "0.3.23"
source = "registry+https://github.com/rust-lang/crates.io-index"

Output

➜ rm -rf target && cargo clippy                                                                                                                                            ~/tmp/clippy_panic
   Compiling rustc-serialize v0.3.23
   Compiling gcc v0.3.45
   Compiling libc v0.2.21
   Compiling time v0.1.36
   Compiling rand v0.3.15
   Compiling rust-crypto v0.2.36
   Compiling five v0.1.0 (file:///Users/gib/tmp/clippy_panic)
error[E0464]: multiple matching crates for `rustc_serialize`
 --> src/main.rs:2:1
  |
2 | extern crate rustc_serialize;
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: candidates:
  = note: path: /Users/gib/tmp/clippy_panic/target/debug/deps/librustc_serialize-54d2bf33b1d4b0b0.rlib
  = note: crate name: rustc_serialize
  = note: path: /Users/gib/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/lib/librustc_serialize-fde13340fc7641e7.rlib
  = note: crate name: rustc_serialize

error[E0463]: can't find crate for `rustc_serialize`
 --> src/main.rs:2:1
  |
2 | extern crate rustc_serialize;
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate

error: aborting due to 2 previous errors

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:455
note: Run with `RUST_BACKTRACE=1` for a backtrace.
thread 'main' panicked at 'rustc_thread failed: Any', src/libcore/result.rs:859
error: Could not compile `five`.

To learn more, run the command again with --verbose.

[oli-obk]

Does building with cargo rustc work? I don't think cargo clippy does anything special.

[gibfahn]

Yep, building works fine:

➜  clippy_panic git:(master) cargo run                                                                            ~/tmp/clippy_panic
    Finished dev [unoptimized + debuginfo] target(s) in 0.0 secs
     Running `target/debug/clippy_panic`
Use toHex: ff

I made a repo for the source in case you wanted to try it out: https://github.com/gibfahn/clippy-panic

cargo clippy fails consistently for me.

[oli-obk]

cargo rustc works differently from cargo run! We forward to cargo rustc, so if cargo rustc also fails, we can't do anything about it.

[oli-obk]

I made a repo for the source in case you wanted to try it out: https://github.com/gibfahn/clippy-panic

Thanks, trying it now

[gibfahn]

Oh sorry, I assumed cargo build called cargo rustc behind the scenes. cargo rustc also passes:

➜  clippy_panic git:(master) cargo rustc                                                                          ~/tmp/clippy_panic
   Compiling libc v0.2.21
   Compiling gcc v0.3.45
   Compiling rustc-serialize v0.3.23
   Compiling rand v0.3.15
   Compiling time v0.1.36
   Compiling rust-crypto v0.2.36
   Compiling clippy_panic v0.1.0 (file:///Users/gib/tmp/clippy_panic)
    Finished dev [unoptimized + debuginfo] target(s) in 11.20 secs

[oli-obk]

We additionally pass -L target/debug/deps -Zno-trans --cfg 'feature="cargo-clippy"' to the cargo rustc call. The -L is the cause most likely. Looks like a legacy thing. I'll check if we can remove it.

[gibfahn]

That seems like the issue, cargo rustc passes, but:

cargo rustc -- -L target/debug/deps -Zno-trans --cfg 'feature="cargo-clippy"' 

Fails with the above error.

[oli-obk]

It's a remnant from the time when we needed the clippy plugin to run cargo clippy. Nowadays cargo-clippy contains all the lints itself and injects them into the rustc call.