These examples:

Ex 1:
abstract class A2<T>{
    abstract <S> S foo(S x, S y);
    abstract <S1> void baz(A2<S1> a);

    void bar(A2<Integer> y, A2<Long> x){
         baz(foo(x, y));
    }
}

Ex 2:
abstract class A<T>{
    abstract <S> S foo(S x, S y);
    <S extends Number & Comparable<? extends Number>> void baz(A<S> a){}

    void bar(A<Long> x, A<Integer> y){
        baz(foo(x, y));
    }
}

Ex 3:
abstract class A1<T>{
    abstract <S> S foo(S x, S y);
    <T extends Number & Comparable<?>, S extends Number & Comparable<?
extends T>> void baz(A1<S> a){}

    void bar(A1<Long> x, A1<Integer> y){
        baz(foo(x, y));
    }
}

compiles in 6 and 7 but fails to compile in 8.

reported by anna.kozlova_at_jetbrains.com in lambda-dev