Possibly bad 'unused import' warning

[steveklabnik]

I get this when compiling:

/Users/steve/src/rust/src/libcore/vec.rs:25:15: 25:23 warning: unused import [-W unused-imports (default)]
/Users/steve/src/rust/src/libcore/vec.rs:25 use old_iter::{BaseIter, CopyableIter};
                                                           ^~~~~~~~

But if I remove these imports, I get an error:

/Users/steve/src/rust/src/libcore/vec.rs:329:28: 329:56 error: type `&['a]` does not implement any method in scope named `to_vec`
/Users/steve/src/rust/src/libcore/vec.rs:329                 result.push(slice(v, start, i).to_vec());
                                                                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/steve/src/rust/src/libcore/vec.rs:334:16: 334:45 error: type `&['a]` does not implement any method in scope named `to_vec`
/Users/steve/src/rust/src/libcore/vec.rs:334     result.push(slice(v, start, ln).to_vec());
                                                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/steve/src/rust/src/libcore/vec.rs:353:28: 353:56 error: type `&['a]` does not implement any method in scope named `to_vec`
/Users/steve/src/rust/src/libcore/vec.rs:353                 result.push(slice(v, start, i).to_vec());
                                                                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/steve/src/rust/src/libcore/vec.rs:360:16: 360:45 error: type `&['a]` does not implement any method in scope named `to_vec`
/Users/steve/src/rust/src/libcore/vec.rs:360     result.push(slice(v, start, ln).to_vec());
                                                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/steve/src/rust/src/libcore/vec.rs:378:28: 378:58 error: type `&['a]` does not implement any method in scope named `to_vec`
/Users/steve/src/rust/src/libcore/vec.rs:378                 result.push(slice(v, i + 1, end).to_vec());
                                                                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/steve/src/rust/src/libcore/vec.rs:383:16: 383:43 error: type `&['a]` does not implement any method in scope named `to_vec`
/Users/steve/src/rust/src/libcore/vec.rs:383     result.push(slice(v, 0u, end).to_vec());
                                                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/steve/src/rust/src/libcore/vec.rs:403:28: 403:59 error: type `&['a]` does not implement any method in scope named `to_vec`
/Users/steve/src/rust/src/libcore/vec.rs:403                 result.push(slice(v, i + 1u, end).to_vec());
                                                                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/steve/src/rust/src/libcore/vec.rs:410:16: 410:43 error: type `&['a]` does not implement any method in scope named `to_vec`
/Users/steve/src/rust/src/libcore/vec.rs:410     result.push(slice(v, 0u, end).to_vec());

I'm not sure if this is a problem in the warning check, or what, but figured I'd raise the issue.

[alexcrichton]

I'll take a look at this, is this on the current incoming? If you've got a specific revision, that'd be awesome!

I know that without prelude injection things get weird, and I was never quite sure why...

[steveklabnik]

Yes, on the current incoming, and with incoming + all my 'remove warnings' PRs that bors is building.

[steveklabnik]

Oh, I should mention that this happens in stage2:

cp: x86_64-apple-darwin/stage2/lib/librust.dylib
cp: x86_64-apple-darwin/stage2/bin/rust
compile_and_link: x86_64-apple-darwin/stage2/lib/rustc/x86_64-apple-darwin/lib/libcore.dylib
/Users/steve/src/rust/src/libcore/vec.rs:25:15: 25:23 warning: unused import [-W unused-imports (default)]
/Users/steve/src/rust/src/libcore/vec.rs:25 use old_iter::{BaseIter, CopyableIter};
                                                           ^~~~~~~~

[alexcrichton]

This is probably just a stage0 thing where resolve changed. Try doing #[cfg(stage0)] front of including BaseIter, and it should compile (I can verify later if you're unable to, I can't right now)

[steveklabnik]

Is that a good idea, or is it the kind of thing where the next snapshot will make it go away?

[alexcrichton]

I just looked into this, and I think that you were removing the entire import. Just the BaseIter import needed to be removed, not the CopyableIter

[alexcrichton]

This was removed in #6648