Visible compiler "note" from dependency

[SimonSapin]

Usually, warnings and other compiler output from building non-path dependencies is hidden by Cargo. With cargo 0.0.1-pre-nightly (9f265c8 2015-03-25) (built 2015-03-25) and rustc 1.0.0-nightly (27901849e 2015-03-25) (built 2015-03-26), when libc is a dependency, one line of output is not hidden:

rust-cssparser% cargo test -j1 
   Compiling text_writer v0.1.9
   Compiling libc v0.1.3
note: use an identifier not in quotes instead
   Compiling rustc-serialize v0.3.7
[…]

[SimonSapin]

(It’s possible that the root cause is in rustc, maybe in std, but I’m filing this here because it superficially looks like a Cargo issue.)

[alexcrichton]

Yes this is unfortunately a rustc "bug". What's actually happening here is that libc has extern crate "std" as std which the compiler is generating a warning for (deprecated syntax). This warning is accompanied with the note that you see. The compiler also, however, has logic to suppress all warnings on -Awarnings (which Cargo is passing), it just doesn't understand how to suppress the note as well.

You can see rust-lang/rust#23782 for a fix!