The following program does not compile.

If the enclosing instance is explicitly specified, the compiler accepts
the input. (Remove the "BAD" line and uncomment the "OK" line.)
In this case, the compiler correctly implements JLSr2 15.9.2 "Determining
Enclosing Instances".

Note that the compiler already does the right thing with method and field
references into enclosing instances. In the example below, the equivalent
"newInner" method works fine in all cases.

class foo {
    class Inner1 {
    }
    class Inner2 {
        Inner2(Inner1 ignore) {}
        Inner2() {
            this(new Inner1()); //BAD
/// ^
///foo.java:7: cannot reference this before supertype constructor has been called
///
            //this(foo.this.new Inner1()); //OK
        }
        Inner2(char junk) {
            this(newInner1()); //OK
        }
        Inner2(byte junk) {
            this(foo.this.newInner1()); //OK
        }
    }
    Inner1 newInner1() { return new Inner1(); }
}