private int spaceEnd(int start) {
    assert s.charAt(start) == ' ' || s.charAt(start) == '\n';
    int i;
    for (i = start + 1; i < s.length() && s.charAt(i) == ' '; i++) {}
    return i;
  }
Returns the position at which this token ends and the next token begins.
value/src/main/java/com/google/auto/value/processor/JavaScanner.java