code: function lexError(message, input, index) {
  	let lexMessage = message + "\n\n";
  
  	// Show input characters surrounding the source of the error.
  	for (
  		let i = Math.max(0, index - 16);
  		i < Math.min(index + 16, input.length);
  		i++
  	) {
  		lexMessage += input[i];
  	}
  
  	error(lexMessage);
  }
docs: Logs a lexer error message to the console along with the surrounding
  characters.
  
  @param {string} message
  @param {string} input
  @param {number} index