void addWarning(Element element, PackageWarning kind, String message, String fullMessage)

Adds the warning to the counter, and writes out the fullMessage string if configured to do so.

Source 

void addWarning(Element element, PackageWarning kind, String message,
    String fullMessage) {
  assert(!hasWarning(element, kind, message));
  Tuple2<PackageWarning, String> warningData = new Tuple2(kind, message);
  _warningCounts.putIfAbsent(kind, () => 0);
  _warningCounts[kind] += 1;
  _countedWarnings.putIfAbsent(element, () => new Set());
  _countedWarnings[element].add(warningData);
  _writeWarning(kind, fullMessage);
}