An inconsistent detection result of rule SA_FIELD_SELF_ASSIGNMENT

[vanguard-1024]

Hi, I found an inconsistent detection result about the rule SA_FIELD_SELF_ASSIGNMENT, the code example is below. SpotBugs can detect the bug in line 4, but cannot in line 8. These two lines are equivalent, hence, I think this is a false negative.

public class C {
    int foo;
    void foo1() {
        foo = foo++;  // can report a warning in this line
    }
    class subC {
        void foo2() {
            foo = foo++; // should report a warning in this line
        }
    }
}

SpotBugs version: 4.7.1

[baloghadamsoftware]

@vanguard-1024 I made a PR to fix this.