non-reference pattern used to match a reference (see issue #42640)

[zigguratvertigo]

Hi!

On grabbing 0.2.9 from crates.io last night, I hit the following error several times as it tries to compile structopt-derive:

error[E0658]: non-reference pattern used to match a reference (see issue #42640)
--> C:...\structopt-derive-0.2.9\src\attrs.rs:112:17
|
112 | / NameValue(MetaNameValue {
113 | | ident,
114 | | lit: Str(value),
115 | | ..
116 | | }) => self.push_str_method(&ident.to_string(), &value.value()),
| |__________________^
help: consider using a reference

Known issue?

[TeXitoi]

Looks like a direct deps of rust 1.26

[TeXitoi]

what's your rust version? Is updating to latest stable fix this problem?

[hcpl]

@zigguratvertigo the code you pointed to uses default binding modes, implemented a while ago and stabilized in Rust 1.26.

On the related note, I'd like to know what is the policy around minimum supported Rust version for structopt. clap has the policy written down in this issue: clap-rs/clap#740 and it is enforced using Travis CI. @TeXitoi thoughts?

[TeXitoi]

No policy for the moment, but it can be added. I think at minimum, we should add a specific version in .travis.yml to catch the needed rust upgrades.

[TeXitoi]

Maybe "must compile if latest clap compiles" a good policy?

[hcpl]

This sounds reasonable to me. The latest clap tracks 1.21 which should cover enough users targeting CLI apps.

I also suggest placing a short note about required Rust version in README and/or other easily visible places.

[zigguratvertigo]

@TeXitoi updating to latest 1.56.2 fixed the compilation issue - thanks.
Having a check around the minimum supported rust version would be great.