Java generics warning requiring guru meditation

Question

I have some Java code like the following snippet (the example is simplified from the original code). A yellow squiggle and warning message appear, as indicated by the code comment below. The message is: "This method invocation is unsafe since the passed arguments may be of a wrong type."

abstract class Seek<T> {
    abstract <S> Seek<S> seek(S... o);
    abstract <T2> void map(Func<T,T2> call);
    interface Func<I,O> {
        public O call(I x);
    }
    public <X2> void go(Func<T,X2> c, T some) {
        seek(some).map(c); // <- yellow squiggle here on 'c'
    }
}

Why does the warning appear? What is the best way to fix this?

Note: I'm using the AIDE development environment for Android.

EDIT: I fixed an error in the code after reading the answer from @tsolakp and @LouisWasserman.

Answer 1

Actually there are three warnings in that code:

1. Type safety: Potential heap pollution via varargs parameter o at abstract <S> Seek<S> seek(S... o);

2. The type parameter T is hiding the type T at abstract <T,T2> void map(Func<T,T2> call);

3. Type safety: A generic array of X1 is created for a varargs parameter at seek(some).map(c);

It can be clean of warnings A. take out varargs parameter from generic like:

abstract class Seek<T> {
   abstract <S> Seek<S> seek(S o); // <- no more yellow squiggle
   abstract <T1,T2> void map(Func<T1,T2> call); // <- no more yellow squiggle
   interface Func<I,O> {
      public O call(I x);
   }
   public <X1,X2> void go(Func<X1,X2> c, X1 some) {
      seek(some).map(c); // <- no more yellow squiggle here on 'c'
   }
 }

B. define arrays explicitly like:

  abstract class Seek<T> {
  abstract <S> Seek<S> seek(S[] o);        // <- no more yellow squiggle
  abstract <T2> void map(Func<T,T2> call); // <- no more yellow squiggle
  interface Func<I,O> {
    public O call(I x);
  }
  public <X1,X2> void go(Func<X1,X2> c, X1[] some) {
    seek(some).map(c); // <- no more yellow squiggle
  }
}

but, S[] o is quite not the same as S... o. It can take only Array explicitly. Maybe you need to reconsider your design?

IMHO: I really do not understand needs to have that many Generic type parameters at the same time on class and methods level...