`needless_collect` has no understanding of lifetimes

[awused]

Summary

needless_collect doesn't consider if the iterator is borrowing values that are moved between the collect call and where the collected values are used.

Lint Name

needless_collect

Reproducer

I tried this code:

fn main() {
    let original = vec![1, 2];

    let copied: Vec<_> = (&original).iter().copied().collect();
    drop(original);

    copied.into_iter().for_each(|e| println!("{e:?}"));
}

I saw this happen:

needless_collect suggests this code, which references original after I explicitly move it and the suggestion does not compile.

fn main() {
    let original = vec![1, 2];


    drop(original);

    (&original).iter().copied().for_each(|e| println!("{e:?}"));
}

I expected to see this happen:

needless_collect should not fire here since originals does is moved after the collect call but before the into_iter call that it wants to eliminate.

Version

rustc 1.62.0 (a8314ef7d 2022-06-27)
binary: rustc
commit-hash: a8314ef7d0ec7b75c336af2c9857bfaf43002bfc
commit-date: 2022-06-27
host: x86_64-unknown-linux-gnu
release: 1.62.0
LLVM version: 14.0.5

Additional Labels

@rustbot label I-suggestion-causes-error