JDK-8232931 could be hiding this bug from showing up: From code review of com.sun.tools.javac.comp.LambdaToMethod.LambdaAnalyzerPreprocessor#visitClassDef, I suspect that we may have trouble with properly translating this code:


public class X {
    Object foo() {
        int x = 42;
        System.out.println("In foo");
        Object goo() {
            System.out.println("In goo");
            class Y {
            }
            return new Y();
        }
        return goo();
    }
    public static void main(String [] args) {
        Object o = new X().foo();
        System.out.println(o);
    }
}

This is because, if a class is defined within a local method, the local method must capture its enclosing instance (if any) as it does for classes within a lambda. The relevant code triggers only for
lambda enclosure case since it is guarded by

if (directlyEnclosingLambda() != null) {

}