Type inference error when generic class constructor builds an instance of another generic class with bounded type

When type parameter is bounded (T extends Comparable<? super T>), I encounter a type inference problem using <> to let the compiler infer the type in the following example:

import java.util.Comparator;
import java.util.Set;
import java.util.TreeSet;

public class InferTypeArgApp {
    static class ACollection<E extends Comparable<? super E>> {
    // static class ACollection<E> {  // <-- If E isn't bounded, BCollection can use <>
        private Set<E> mySet;

        ACollection(Comparator<? super E> comparator) {
            mySet = new TreeSet<>(comparator);
        }
    }

    static class BCollection<E extends Comparable<? super E>> {
        private ACollection<E> myACollection;

        BCollection(Comparator<? super E> comparator) {
            myACollection = new ACollection<>(comparator);
            //              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ <-- Cannot infer type
            //                                                arguments for
            //                                                ACollection<>Java(16778094)
            //
            // myACollection = new ACollection<E>(comparator);  // <-- This works
        }
    }

    public static void main(String[] args) {
        ACollection<Integer> col = new ACollection<>(null); // <-- Java manages to
                                                            //     implicitly infer
                                                            //     the type here
    }
}

If I declare ACollection as class ACollection<E extends Comparable<? super E>> then I get the type argument inference error. However, if it’s declared as class ACollection<E> then there is no error.

The way I see it, Java compiler has enough information to infer that ACollection I initialize in BCollection constructor has type argument E regardless of whether ACollection type argument extends anything.

Why is there a type inference error?

For completeness, here is the full compilation error which didn’t clarify anything for me but hopefully someone can parse it:

$ /usr/local/java/jdk/bin/javac -Xdiags:verbose InferTypeArgApp.java
InferTypeArgApp.java:20: error: cannot infer type arguments for ACollection<>
            myACollection = new ACollection<>(comparator);
                            ^
  reason: cannot infer type-variable(s) E#1
    (argument mismatch; Comparator<CAP#1> cannot be converted to Comparator<? super E#3>)
  where E#1,E#2,E#3 are type-variables:
    E#1 extends Comparable<? super E#1> declared in class ACollection
    E#2 extends Comparable<? super E#2> declared in class BCollection
    E#3 extends CAP#1,Comparable<? super E#3>
  where CAP#1 is a fresh type-variable:
    CAP#1 extends Object super: E#2 from capture of ? super E#2
1 error

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