static LS tok_moveImportsUp(L<S> tok) {
  new StringBuilder buf;
  
  //print("tok_moveImportsUp n=" + l(tok));
  //print("Source begins: " + quote(shorten(join(tok), 200)));
  
  // scan imports on top
  int i;
  new Set<S> have;
  for (i = 1; i < l(tok); i += 2)
    if (eq(tok.get(i), 'import)) {
      int j = indexOf(tok, i+2, ";");
      if (j < 0) break;
      S s = joinSubList(tok, i, j+1);
      have.add(s);
      i = j;
    } else break;
  
  //print("tok_moveImportsUp have " + l(have) + " after " + i);
  
  new L<IntRange> reToks;
  
  // scan imports in text
  for (; i < l(tok); i += 2)
    if (eq(tok.get(i), 'import)) {
      int j = indexOf(tok, i+2, ";");
      if (j < 0) continue; // huh?
      S s = joinSubList(tok, i, j+1);
      //print("Found import at " + i + ": " + s);
      if (!have.contains(s)) {
        buf.append(s).append("\n");
        have.add(s);
      }
      replaceTokens(tok, i, j+1, "");
      ifndef tok_moveImportsUp_skipMostReToks
        reToks.add(intRange(i, j+1));
      endifndef
      i -= 2;
    }
    
  if (nempty(buf)) {
    if (l(tok) == 1) addAll(tok, "", "");
    tok.set(1, str(buf)+"\n"+tok.get(1));
    reToks.add(intRange(1, 2));
  }
    
  ret reTok_multi(tok, reToks);
}

Began life as a copy of #1009579