Support path prefix which refers to per-user DosDevices ("\??\C:\...")

[kgv]

std::path::Prefix does not support windows prefixes like \??\C:\....

See more about prefix which refers to per-user DosDevices

#![allow(unused)]
use std::path::{Component, Path, Prefix};
fn main() {
    let path = Path::new(r"\??\C:\Users\Rust\Pictures\Ferris");
    assert!(path.is_absolute());
}

(Playground)

Errors:

   Compiling playground v0.0.1 (/playground)
    Finished dev [unoptimized + debuginfo] target(s) in 0.61s
     Running `target/debug/playground`
thread 'main' panicked at 'assertion failed: path.is_absolute()', src/main.rs:7:5
note: Run with `RUST_BACKTRACE=1` for a backtrace.

[retep998]

You should be using \\?\ instead of \??\. However it may be a good idea to treat \??\ like \\?\ in Rust.

[DemiMarie]

It is a good idea.