// token range is from function name to closing bracket+1
static TokenRange tok_findFunctionCall(LS tok, S functionName) {
  int idx = jfind(tok, functionName + "(");
  if (idx < 0) null;
  int iOpening = tok.indexOf("(", idx);
  int iEnd = findEndOfBracketPart(tok, iOpening);
  ret new TokenRange(idx, iEnd);
}