Function is_windows_absolute 

pub fn is_windows_absolute(s: &str) -> bool

True iff s is a fully-qualified Windows absolute path: a drive letter, a colon, and a path separator (C:\dir or C:/dir). This is the STRICT sense used when “absolute” must mean root-anchored, e.g. deciding whether a path is already absolute for URI formatting. The drive-relative C:rel is NOT absolute and returns false.