code: private void doPercentTypedAccounting(Node n) {
      JSType type = n.getJSType();
      if (type == null) {
        nullCount++;
      } else if (type.isUnknownType()) {
        if (reportUnknownTypes) {
          compiler.report(JSError.make(n, UNKNOWN_EXPR_TYPE));
        }
        unknownCount++;
      } else {
        typedCount++;
      }
    }
docs: Counts the given node in the typed statistics.
  
  @param n a node that should be typed