Unused imports not detected in dependencies

[bfops]

I believe the following set-up should trigger unused import warnings in dep/dep.rs, but it doesn't!

rustc 0.12.0-pre-nightly (2e92c67 2014-08-28 23:56:20 +0000)

Cargo.toml:

[package]

name = "testbed"
version = "0.0.0"
authors = []

[[bin]]

name = "testbed"
path = "./main.rs"

[dependencies.dep]
name = "dep"
path = "dep"

main.rs:

#[main]
pub fn main() {
}

dep/Cargo.toml:

[package]
name = "dep"
version = "0.0.0"
authors = []

[lib]
name = "dep"
path = "dep.rs"

dep/dep.rs:

use std::iter;

[ftxqxd]

I don’t think this is a bug in Rust, just a bug in Cargo. I believe Cargo silences the output of compiling dependencies unless they fail. Running cargo build --verbose gives the command it runs:

rustc dep/dep.rs --crate-name dep --crate-type lib -C metadata=deadbeefdeadbeef -C extra-filename=-deadbeefdeadbeef --out-dir target/deps --dep-info target/.fingerprint/dep-deadbeefdeadbeef/dep-lib-dep -L target/deps -L target/deps

Running this command manually gives the warning as it should.

Moreover, if dep/dep.rs contains an error that occurs after the unused import warning does:

use std::iter;

pub fn f() {
    let _x: Box<str> = box *"hello world";
}

then the warning is printed correctly, followed by the error this code causes (in this case, an ICE).

[alexcrichton]

Yes, this belongs in the cargo repository. Currently cargo captures all output of the compiler (intentionally) for dependencies, and does not print it by default (which causes the behavior you're seeing).

[bfops]

Good point! My mistake, thanks! I'll report it on cargo.