rustc -g file.rs does not work

[pnkfelix]

After PR #12714, the -g option to rustc stopped working robustly.

Basically, it seems to gobble up any succeeding token as the numeric argument setting the debuginfo level, so you cannot pass -g immediately before the input file name.

Here is an example of the breakage:

% rustc /tmp/hw.rs -g
% rustc -g /tmp/hw.rs
error: no input filename given
% rustc -g=2 /tmp/hw.rs
error: debug info level needs to be between 0-2
% rustc -g 2 /tmp/hw.rs
% rustc -g2 /tmp/hw.rs
% 

My recommended fix: split the options so that --debuginfo requires the level parameter, while -g does not accept a level parameter (and instead always has the same effect as --debuginfo 2).

[michaelwoerister]

There's already some discussion about this problem on reddit.
I'd prefer if libgetopts had a way of robustly handling optional arguments but implementing that with a nice, non-hacky interface would probably mean more work than I want to spend on this at the moment.
I think your proposed fix (also suggested on reddit by @SiegeLord) seems like a good solution for the time being.