getopts copy parameters

[Aatch]

Rust 0.4 throws warnings about non-implicitly copyable types when using getopts in (what I consider) to be normal usage

let matches = match getopts(args, opts) {
   result::Ok(m)  => copy m, //Need to copy... Not expected, but understandable
   result::Err(f) => fail fail_str(copy f) //Need to copy here too, but it's a failure!
}

let thing = if opt_present(copy matches, "o") { // Not expected here either
    "o given"
} else {
    "o not given"
}

I'm sure some of it is me failing at the language, but it's a major toe-stub since I'm not expecting to have to copy everything around, especially when I'm not expecting any of the functions to change the data.

[Dretch]

I think some of those copy could be move instead - which would avoid the can't-copy warnings, because a move is not considered a copy. You might also need to use move patterns - e.g. result::Ok(move m) => ....

[Aatch]

Some of them could be moves, it's more the opt_* functions requiring copies, I can't see anything that alters the matches. To some extent I imagine the matches to be completely immutable and therefore the idea that I need to copy it around seems... ugly.

I think it's just a side-effect from implicit copy being either a warning or error now (not sure which), where as before it was silent. I think it's better to make it explicit, but also re-working the functions, especially libstd functions to avoid copying would be nice as well.

[catamorphism]

I'm about to submit a pull request to change the opt_ functions to take references to a vector matches, which obviates the need for copying. For example, this will work:

extern mod std;

use std::getopts::*;

fn main() {
    let args = ~[];
    let opts = ~[optopt(~"b")];

    match getopts(args, opts) {
        result::Ok(ref m)  =>
            assert !opt_present(m, "b"),
        result::Err(f) => fail fail_str(f)
    };

}

Two things to watch out for : you have to use the ref keyword when matching on the result of getopts, and since the result will be a borrowed pointer into the argument vector to getopts, you have to use it within the proper scope (above, I'm using it in the action for the first pattern in the match, but I wouldn't be able to use it outside the match).

[catamorphism]

Fixed in 082a88e