extensions/assistedinject/src/com/google/inject/assistedinject/FactoryProvider2.java
@Override
  @SuppressWarnings("unchecked")
  public Collection<AssistedMethod> getAssistedMethods() {
    return (Collection<AssistedMethod>) (Collection<?>) assistDataByMethod.values();
  }
@Override
  @SuppressWarnings("unchecked")
  public Collection<AssistedMethod> getAssistedMethods() {
    return (Collection<AssistedMethod>) (Collection<?>) assistDataByMethod.values();
  }
the collection is immutable.