Function replace_with_pad_left_char 

pub fn replace_with_pad_left_char<'a, C>(
    s: &'a mut str,
    r: &str,
    pad_char: C,
) -> Result<&'a mut str, ReplaceWithPadCharError>
where
    C: Into<char>,

Replace the str with another of the same length or shorter, right aligned. The remaining bytes before the str will be filled with char, which must be one byte long.

use mut_str::replace_with_pad_left_char;

let mut owned_s = Box::<str>::from("World!");

replace_with_pad_left_char(&mut *owned_s, "🌍", '!').unwrap();
assert_eq!(&*owned_s, "!!🌍");

replace_with_pad_left_char(&mut *owned_s, "aaaa", 'b').unwrap();
assert_eq!(&*owned_s, "bbaaaa");

Errors

• If pad_char, when utf8 encoded, is longer than Self, ReplaceWithPadCharError::PadCharTooLong will be returned.
• If r, when utf8 encoded, is longer than s, when utf8 encoded, ReplaceWithPadCharError::ReplacementLen will be returned.