Compiler warnings are not raised for code enclosed in macros

[cskr]

When deprecated API usage is enclosed in a macro like try!, no warning is raised. However, using it directly in match does.

Below is an example using the deprecated url crate from rust nightly distribution. A warning is raised only in the use_match function.

extern crate url;

use url::Url;

fn main() {
    println!("Host: {}", use_try("http://localhost").unwrap())
    println!("Host: {}", use_match("http://localhost").unwrap())
}

fn use_try(s: &str) -> Result<String, String> {
    let u = try!(Url::parse(s));
    Ok(u.host)
}

fn use_match(s: &str) -> Result<String, String> {
    return match Url::parse(s) {
        Ok(u) => Ok(u.host),
        Err(e) => Err(e)
    }
}

[huonw]

cc @aturon (I think this is probably related to squashing stability warnings for macro generated code, it apparently includes arguments passed in).

[aturon]

Thanks for the heads up. Right now all expanded code is ignored. It might be possible, at least for macros-by-example, to track the "provenance" of code being produced and warn on code that was supplied by the macro user. I have no idea how hard that would be to do, though.

[cskr]

@aturon What are "macros-by-example"?

[huonw]

@tuxychandru macros declared with macro_rules! ... { ... }.