False report on same item is being pushed into this Vec

[himajin2045]

I tried this code:

fn main() {
    let v1 = vec![Some(1), Some(2), Some(3), None];
    let mut v1_iter = v1.iter();
    let mut v2 = Vec::new();
    for _ in 0..3 {
        let a = match v1_iter.next() {
            Some(a) => a,
            None => break,
        };
        v2.push(a);
    }
    println!("items are not the same: {:#?}", v2);
}

I expected to see this happen:

No warnings.

Instead, this happened:

Clippy warns:

warning: it looks like the same item is being pushed into this Vec
  --> src/main.rs:10:9
   |
10 |         v2.push(a);
   |         ^^
   |
   = note: `#[warn(clippy::same_item_push)]` on by default
   = help: try using vec![a;SIZE] or v2.resize(NEW_SIZE, a)
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#same_item_push

warning: 1 warning emitted

Meta

• cargo clippy -V: clippy 0.0.212 (7e6d6e5 2020-08-16)
• rustc -Vv:

rustc 1.47.0-nightly (7e6d6e5f5 2020-08-16)
binary: rustc
commit-hash: 7e6d6e5f535321c2223f044caba16f97b825009c
commit-date: 2020-08-16
host: x86_64-apple-darwin
release: 1.47.0-nightly
LLVM version: 10.0

Backtrace

<backtrace>

[ebroto]

Hey @himajin2045, thanks for your report!

I can't reproduce this false positive in the playground.

This was fixed in #6016, and backported to 1.47 in rust-lang/rust#77403. Your Clippy version seems older (2020-08-16), so I think that if you update Clippy you will get rid of that false positive.

Feel free to reopen if the suggested fix does not work for you!