XO0150: character that cannot start any token

The lexer found a character that begins no Xo token, such as @ or a stray Unicode symbol outside a string or comment. Xo source is UTF-8 and identifiers are [A-Za-z_][A-Za-z0-9_]*. Remove the character or move it into a string literal. See core 1.1 and 1.5.

Example

fn f(x: Int) -> Int {
  x @
}

Fix

fn f(x: Int) -> Int {
  x
}

Run xo explain XO0150 for this text in a terminal, or see section 10.6 of the specification.