code: private void checkNamespaces() {
      for (Name name : nameMap.values()) {
        if (name.isNamespaceObjectLit()
            && (name.getAliasingGets() > 0
                || name.getLocalSets() + name.getGlobalSets() > 1
                || name.getDeleteProps() > 0)) {
          boolean initialized = name.getDeclaration() != null;
          for (Ref ref : name.getRefs()) {
            if (ref == name.getDeclaration()) {
              continue;
            }
  
            if (ref.type == Ref.Type.DELETE_PROP) {
              if (initialized) {
                warnAboutNamespaceRedefinition(name, ref);
              }
            } else if (
                ref.type == Ref.Type.SET_FROM_GLOBAL
                || ref.type == Ref.Type.SET_FROM_LOCAL) {
              if (initialized && !isSafeNamespaceReinit(ref)) {
                warnAboutNamespaceRedefinition(name, ref);
              }
  
              initialized = true;
            } else if (ref.type == Ref.Type.ALIASING_GET) {
              warnAboutNamespaceAliasing(name, ref);
            }
          }
        }
      }
    }
docs: Runs through all namespaces (prefixes of classes and enums), and checks if any of them have
  been used in an unsafe way.