Description:
------------
The source code below doesn't compile, fails with following error. According to this error the type of varValue is inferred by compiler as 'A<? super A<? super Object>>'. However according to the specification it should have been A<? super A<? extends Integer>> .

Compilation output:
-------------------
Test.java:15: error: incompatible types: A<CAP#1> cannot be converted to A<? super A<? extends Integer>>
        A<? super A<? extends Integer>> expectedTypeValue = varValue;
                                                            ^
  where CAP#1 is a fresh type-variable:
    CAP#1 extends Object super: A<? super Object> from capture of ? super A<? super Object>
1 error


Soure code:
-----------
class A<E> { }

public class Test {

  <T> A<? super T> m(T t) {
      return null;
  }

  <U> A<? super A<? extends U>> m2(A<? super U> u) {
    return null;
  }

  void test() {
    var varValue = m2(m(10));
A<? super A<? extends Integer>> expectedTypeValue = varValue;
  }
}




Type of var is inferred as follows:
-----------------------------------

1. Type variable U in method m2 is inferred by applying Invocation Type Inference (18.5.2) as 'Integer <: Y1 <: Object'

2. As per chapter 15.12.3 capture conversion is applied to the return type: A<? super A<? extends U>> [U:=Y1]

Capture_conversion(A<? super A<? extends Y1>>) --> A< [A<? extends Y1> <: CAP <: Object>] >

3. Type of varValue results from applying upward projection to A< [A<? extends Y1> <: CAP <: Object>] > :

T = A< [A<? extends Y1> <: CAP <: Object >] >

4. We proceed to following assertion:
    
If T is a parameterized class type or a parameterized interface type, G<A1, ..., An>, then the result is G<A1', ..., An'>, where, for 1 ≤ i ≤ n, Ai' is derived from Ai as follows:

A1 = [A<? extends Y1> <: CAP <: Object]

5. We proceed to following assertion:

If Ai is a type that mentions a restricted type variable, then Ai' is a wildcard. Let U be the upward projection of Ai. There are three cases:

U = upward_projection([A<? extends Y1> <: CAP <: Object]) = upward_projection(Object) = Object

So U = Object

6. Since U is Object, we proceed to the following assertion:

Otherwise, if the downward projection of Ai is L, then Ai' is a lower-bounded wildcard, ? super L.

    L = Downward_projection([A<? extends Y1> <: CAP <: Object]) = Downward_projection(A<? extends Y1>)

6.1. So we proceed to following assertion:

If T is a parameterized class type or a parameterized interface type, G<A1, ..., An>, then the result is G<A1', ..., An'>, if, for 1 ≤ i ≤ n, a type argument Ai' can be derived from Ai as follows; if not, the result is undefined:

A1 = ? extends [Integer <: Y1 <: Object]

6.2. So eventually we come to the following assertion:

If Ai is an upper-bounded wildcard that mentions a restricted type variable, then if the downward projection of the wildcard bound is U, then Ai' is a wildcard ? extends U; if the downward projection of the wildcard bound is undefined, then Ai' is undefined.

U = Downward_projection([Integer <: Y1 <: Object]) = Downward_projection(Integer) = Integer
So, U = Integer
A1' = ? extends Integer


6.3. So, Downward_projection([A<? extends Y1> <: CAP <: Object]) = A<? extends Integer>

7. So we return to the calculation of upward projection.
    
L = A<? super Integer>
A1' = ? super L = ? super A<? extends Integer>

8. Upward_projection(A< [A<? extends Y1> <: CAP <: Object] ) = A<A1'> = A<? super A<? extends Integer>>

Type of varValue is inferred as A<? super A<? extends Integer>>