regex! is generating unused code warnings

[wycats]

src/cargo/mod.rs:9:1: 9:27 note: in expansion of regex!
src/cargo/sources/git.rs:42:21: 42:55 note: expansion site
src/cargo/sources/git.rs:42:21: 42:55 warning: code is never used: `add_empty`, #[warn(dead_code)] on by default
src/cargo/sources/git.rs:42         let regex = regex!(r"^\* (?P<branch>.*)\s*$");
                                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/cargo/mod.rs:9:1: 9:27 note: in expansion of regex!
src/cargo/sources/git.rs:42:21: 42:55 note: expansion site
src/cargo/sources/git.rs:42:21: 42:55 warning: code is never used: `contains`, #[warn(dead_code)] on by default
src/cargo/sources/git.rs:42         let regex = regex!(r"^\* (?P<branch>.*)\s*$");
                                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/cargo/mod.rs:9:1: 9:27 note: in expansion of regex!
src/cargo/sources/git.rs:42:21: 42:55 note: expansion site
src/cargo/sources/git.rs:42:21: 42:55 warning: code is never used: `empty`, #[warn(dead_code)] on by default
src/cargo/sources/git.rs:42         let regex = regex!(r"^\* (?P<branch>.*)\s*$");
                                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/cargo/mod.rs:9:1: 9:27 note: in expansion of regex!
src/cargo/sources/git.rs:42:21: 42:55 note: expansion site
src/cargo/sources/git.rs:42:21: 42:55 warning: code is never used: `pc`, #[warn(dead_code)] on by default
src/cargo/sources/git.rs:42         let regex = regex!(r"^\* (?P<branch>.*)\s*$");
                                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/cargo/mod.rs:9:1: 9:27 note: in expansion of regex!
src/cargo/sources/git.rs:42:21: 42:55 note: expansion site
src/cargo/sources/git.rs:42:21: 42:55 warning: code is never used: `groups`, #[warn(dead_code)] on by default
src/cargo/sources/git.rs:42         let regex = regex!(r"^\* (?P<branch>.*)\s*$");
                                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The source code creates a regex with a named capture and uses it immediately below.

[alexcrichton]

Could you provide some sample code? This doesn't seem to emit warnings in a smaller test case:

#![feature(phase)]
#[phase(syntax)] extern crate regex_macros;
extern crate regex;

fn main() {
    let regex = regex!(r"^\* (?P<branch>.*)\s*$");
}

[huonw]

Just writing fn main() { regex!("..."); } demonstrates the flood of warnings (preferably the warning would be the "unused result that must be used" one, rather than revealing the implementation details of regex!()).

[BurntSushi]

Hmm. I can't reproduce this with @huonw's example.

[huonw]

I'd guess @Kimundi's static regex changes have incidentally fixed this (I'm away from a compiler so can't check/check-in a test).

Flagging as needs-test.

[Kimundi]

Actually, I discovered these warning after I implemented regex in statics. Current example that generates lots of warnings: (tested on playpen)

#![feature(phase)]
#[phase(syntax)]
extern crate regex_macros;
extern crate regex;

static FOO: regex::Regex = regex!("foo");

fn main() {
}

<anon>:6:1: 6:42 warning: code is never used: `FOO`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<anon>:6:28: 6:42 warning: code is never used: `CAP_NAMES`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site
<anon>:6:28: 6:42 warning: code is never used: `exec`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site
<anon>:6:28: 6:42 warning: code is never used: `Nfa`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site
<anon>:6:28: 6:42 warning: code is never used: `run`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site
<anon>:6:28: 6:42 warning: code is never used: `step`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site
<anon>:6:28: 6:42 warning: code is never used: `add`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site
<anon>:6:28: 6:42 warning: code is never used: `Thread`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site
<anon>:6:28: 6:42 warning: code is never used: `Threads`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site
<anon>:6:28: 6:42 warning: code is never used: `new`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site
<anon>:6:28: 6:42 warning: code is never used: `add`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site
<anon>:6:28: 6:42 warning: code is never used: `add_empty`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site
<anon>:6:28: 6:42 warning: code is never used: `contains`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site
<anon>:6:28: 6:42 warning: code is never used: `empty`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site
<anon>:6:28: 6:42 warning: code is never used: `pc`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site
<anon>:6:28: 6:42 warning: code is never used: `groups`, #[warn(dead_code)] on by default
<anon>:6 static FOO: regex::Regex = regex!("foo");
                                    ^~~~~~~~~~~~~~
<anon>:3:1: 3:27 note: in expansion of regex!
<anon>:6:28: 6:42 note: expansion site