core/src/com/google/inject/internal/InjectorImpl.java
private static boolean isMembersInjector(Key<?> key) {
    return key.getTypeLiteral().getRawType().equals(MembersInjector.class)
        && key.getAnnotationType() == null;
  }
private static boolean isMembersInjector(Key<?> key) {
    return key.getTypeLiteral().getRawType().equals(MembersInjector.class)
        && key.getAnnotationType() == null;
  }
Returns true if the key type is MembersInjector (but not a subclass of MembersInjector).