Cargo check does not report `error: symbol `foo` is already defined`

[mcarton]

Problem
Some errors are not reported by cargo check.

Steps
For example, here cargo check succeeds:

% cargo check
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
% cat src/main.rs 
#[no_mangle]
fn test() {}

mod foo {
    #[no_mangle]
    fn test() {}
}

fn main() {
    println!("Hello, world!");
}

But cargo build does fail:

% cargo build
   Compiling asdf v0.1.0 (/tmp/asdf)
error: symbol `test` is already defined
 --> src/main.rs:6:5
  |
6 |     fn test() {}
  |     ^^^^^^^^^^^^

error: aborting due to previous error

error: Could not compile `asdf`.

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

Notes

Output of cargo version:

% cargo --version      
cargo 1.34.0 (6789d8a0a 2019-04-01)
% rustc --version
rustc 1.34.2 (6c2484dc3 2019-05-13)
% rustup --version
rustup 1.18.1 (2019-04-26)

[ehuss]

Moved to rust-lang/rust.

I think this is to be expected. cargo check performs all steps up to translation. Some errors are only detected during later phases. I don't know if it is feasible to check errors like this.

[mcarton]

I understand why it fails, but the intent of cargo check seems to be that if cargo check succeeds, then cargo build will as well, however this is not true, and doesn't seem to be explicitly documented anywhere.

$ cargo check --help
cargo-check 
Check a local package and all of its dependencies for errors

[Mark-Simulacrum]

I think this is essentially unavoidable -- there's a reason cargo build and cargo check are separate; one can do strictly more error checking than the other. I'm going to close this as not a bug.