ExtendInto<Extender=Vec<u8>> appears to have no useful implementors

[ExpHP]

It is unclear to me how to use bytes::complete::escape_transform on bytestrings, because the only implementors of ExtendInto<Extender=Vec<u8>> are [u8] and &[u8], neither of which can be returned without borrowing from the input.

• Rust version : rustc 1.46.0
• nom version : 5.0.0
• nom compilation features used:

Test case

use nom::{
    bytes::complete::{escaped_transform, take, is_not},
    combinator::{map},
};

fn main() {
    let res: nom::IResult<_, _> = escaped_transform(  // Error: ExtendInto is not implemented for u8
        is_not(r#"\""#),
        '\\',
        map(take(1u32), |bytes: &[u8]| match bytes[0] {
            b'n' => b'\n',
            b => b,
        }),
    )(b"sfj\\n\\isoeg");
    assert_eq!(res, Ok((&b""[..], b"sfj\nisoeg".to_vec())))
}

[Geal]

you could replace the closure like this:

|bytes: &[u8]| match bytes[0] {
            b'n' => &b"\n"[..],
            _ => &bytes[..1],
}

[ExpHP]

Okay, this is true, you can use static references if there are only a limited number of escapes.

Is there any particular reason why u8 and Vec<u8> do not implement the trait? They would provide additional power by allowing the values to be constructed at runtime, making it easier to support escapes like "\xXX" for an arbitrary byte. (I think this can be done with static refs but it's a bit janky, as it requires having a static string with all byte values like b"\x00\x01\x02\x03...\xfe\xff" to take slices from)