MyClass is rejected by javac with the following error:

incompatible types
found : java.util.Collection<java.lang.String>
required: java.util.Collection<java.lang.Object>

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import java.util.Collection;

public class MyClass {
public static <E, F extends E> Collection<E> foo(F val) { return null; }

public static void tryIt() { Collection<Object> obj = foo("bar"); }
}