On Mon, 1 Sep 2025 18:12:15 GMT, Archie Cobbs <aco...@openjdk.org> wrote:
>> ok, so I guess I still don't get whether this _must_ be an error. In
>> principle `y` could have a local proxy, in which case the lambda could be
>> thought of as accessing that proxy, so no need to capture `this` ?
>
>> ok, so I guess I still don't get whether this _must_ be an error. In
>> principle `y` could have a local proxy, in which case the lambda could be
>> thought of as accessing that proxy, so no need to capture `this` ?
>
> I wonder what is the mental model supposed to be here.
>
> @mcimadamore what is your opinion on whether this should compile?
>
> class A {
> int y;
> A() {
> y = 1;
> class B {
> static void m() { // static context
> System.out.println(y);
> }
> }
> super();
> }
> }
>
> If your answer is "No" then aren't you then implying that `y` shouldn't be
> available whenever `A.this` is not available? In which case doesn't that
> answer your question?
>
> If your answer is "Yes", then doesn't that imply that _this_ should also
> compile...
>
> class A {
> int y;
> A() {
> y = 1;
> class B {
> static void m() { // static context
> System.out.println(A.this.y);
> }
> }
> super();
> }
> }
>
> even though this doesn't:
>
> class A {
> int y;
> A() {
> y = 1;
> class B {
> static void m() { // static context
> System.out.println(A.this);
> }
> }
> super();
> }
> }
I suppose what I'm saying is: I understand why the code doesn't compile in
today's world. But as we relax more restrictions and we resort to more complex
translation strategies, I do wonder if some of these rules that prevent reads
from lambdas will feel too tight. E.g. imagine the case of a final field --
that is written only once. If we already saw a write for that field, what stops
us from being able to reference it from a lambda -- through a local proxy?
I don't buy the argument that `A.this.y` working implies `A.this`. This is
already not the case in the code added by this PR, where reading an already
written field in a prologue is fine, even through `A.this.y` -- but accessing
`this` of a class from the prologue is never ok (if it was you could pass such
a larval `this` to another method).
-------------
PR Review Comment:
https://git.openjdk.org/valhalla/pull/1523#discussion_r2314445939
