From kaya3 at aston.ac.uk  Fri Aug 17 18:35:14 2018
From: kaya3 at aston.ac.uk (Kay, Andrew (Research Student))
Date: Fri, 17 Aug 2018 18:35:14 -0000
Subject: JLS - "anywhere within" static initializer
Message-ID: <091FE45216766B4689D1F05C421CF18363C7DF24@exch-mb-l4-01.campus.aston.ac.uk>

Hi,

I've noticed something slightly misleading in the JLS, section 8.7 (Static Initializers):
https://docs.oracle.com/javase/specs/jls/se10/html/jls-8.html#jls-8.7

It is a compile-time error if a return statement (?14.17<https://docs.oracle.com/javase/specs/jls/se10/html/jls-14.html#jls-14.17>) appears anywhere within a static initializer.

It is a compile-time error if the keyword this (?15.8.3<https://docs.oracle.com/javase/specs/jls/se10/html/jls-15.html#jls-15.8.3>) or the keyword super (?15.11<https://docs.oracle.com/javase/specs/jls/se10/html/jls-15.html#jls-15.11>, ?15.12<https://docs.oracle.com/javase/specs/jls/se10/html/jls-15.html#jls-15.12>) or any type variable declared outside the static initializer, appears anywhere within a static initializer.

The plain meaning of "anywhere within" would forbid the following code, which has return, this and super within a static initializer (via a local class declaration), but compiles without errors (using version 10.0.2).

class A {
    static int x;
    static {
        class B {
            B() { super(); }
            int y = 1;
            int c() {
                return this.y;
            }
        }
        x = new B().c();
    }
}

This could be resolved by adding something like "?anywhere within a static initializer, unless it appears within a local class declaration contained in that static initializer". There are at least two more cases which should be permitted - anonymous class declarations, and return statements in lambda body blocks.

Thanks,
-Andrew Kay