`manual_flatten` false positives with reference slices

Lint name: manual_flatten

I tried this code:

struct Test {
    a: Option<usize>,
    b: Option<usize>,
}

fn main() {
    let t = Test {
        a: Some(1),
        b: Some(2),
    };

    for x in [&t.a, &t.b] {
        if let Some(y) = x {
            println!("{}", y);     
        }
    }
} 

This also applies to mutable references.

Clippy suggests this, which is both incomplete as a refactor and does not compile. Try as I might I could not get into_iter().flatten() to compile.

for x in [&t.a, &t.b].into_iter().flatten() {
    if let Some(y) = x {
        println!("{}", y);
    }
}

Meta

I saw https://github.com/rust-lang/rust-clippy/issues/6893 which appears to be the same issue, but it was claimed to be fixed there and that fix should have landed in 1.53. I'm on 1.54 now and still seeing it with both mutable and immutable reference slices.

• cargo clippy -V: clippy 0.1.54 (a178d03 2021-07-26)
• rustc -Vv:

rustc 1.54.0 (a178d0322 2021-07-26)
binary: rustc
commit-hash: a178d0322ce20e33eac124758e837cbd80a6f633
commit-date: 2021-07-26
host: x86_64-unknown-linux-gnu
release: 1.54.0
LLVM version: 12.0.1