split_inclusive() on empty slice yields a single empty slice (instead of no slices at all)

[martinvonz]

I tried this code:

    let empty_str = "";
    let expected : Vec<&str> = vec![];
    assert_eq!(empty_str.split_inclusive(|ch| ch == '\n').collect::<Vec<_>>(), expected);
    let empty_slice: &[u8] = &[];
    let expected : Vec<&[u8]> = vec![];
    assert_eq!(empty_slice.split_inclusive(|b| *b == b'\n').collect::<Vec<_>>(), expected);

I expected to see this happen: Both assertions pass, i.e. split_inclusive() yields no results on empty input.

Instead, this happened: The second assertion fails because split_inclusive() on an empty slice yields a single empty element instead of no elements.

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rustc --version --verbose:

cargo 1.57.0-nightly (0121d66aa 2021-09-22)

(Skipping backtrace from template as that doesn't seem relevant.)