rustc doesn't allow -W/--warn more than once

[lucy]

~ > rustc --warn unnecessary-qualification --warn non-camel-case-types hi.rs
error: Option 'warn' given more than once.
task 'rustc' failed at 'explicit failure', /build/rust-git/src/rust/src/librustc/driver/driver.rs:1120
task '<main>' failed at 'explicit failure', /build/rust-git/src/rust/src/librustc/lib.rs:453

-W is supposed to work like -A, -D and -F which can appear multiple times.

[sanxiyn]

I believe this was broken in #6719. Tagging @kud1ing and @bstrie.

[kud1ing]

The change was meant to improve usability, since there was no hint that "-W help" exists.
It should be reverted then.

[thestinger]

If passing it more than once becomes possible, the ability to pass comma-separated warnings should probably be removed. It's strange to have that for lints but not for -Z.

[lucy]

@thestinger How do you pass comma separated warnings?

~ > rustc -W unnecessary-qualification,non-camel-case-types main.rs                                                                                          ↲
error: unknown warn flag: unnecessary_qualification,non_camel_case_types

[thestinger]

@neeee: Ah, it was removed...