Integrated: 8304883: Record Deconstruction causes bytecode error

[Jan Lahoda]

On Mon, 27 Mar 2023 13:46:16 GMT, Jan Lahoda <jlahoda at openjdk.org> wrote:

> Originally, we used to support cases like:
> `case null, String s when s.isEmpty() -> <expression>`
> where `s` could be `null` inside the expression, but the guard was only evaluated when `s != null`. This was implemented by augmenting the guard with `s == null || <original-guard>`.
> 
> This feature has been dropped since then.
> 
> Also note that in other cases, like:
> 
> record R(Object o) {}
> Object o = new R(null);
> switch (o) {
>     case R(var v) when v.toString().isEmpty() -> {}
> }
> 
> 
> We always expected a NPE on dereferencing the binding with value `null` (`v` in this case) in guard.
> 
> But, the code to implement the `case null, <binding>` remained in javac, and is causing problems, because, while the user cannot write `case null, <binding>` anymore, internally the desugaring sometimes generates that (when factoring out common prefixes). And the original code will still augment the guards to `<binding> == null || <guard>`, which causes the variables that are assigned in the guard to not being definitely assigned after the augmented guard.
> 
> The proposal is to simply remove the code that adds `<binding> == null || <guard>`, as there's no case where we would skip guards for `null` bindings anymore.

This pull request has now been integrated.

Changeset: 2aec910e
Author:    Jan Lahoda <jlahoda at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/2aec910ea4bcd3a253a76a70323f9bebb49d8e91
Stats:     67 lines in 2 files changed: 45 ins; 13 del; 9 mod

8304883: Record Deconstruction causes bytecode error

Reviewed-by: vromero

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PR: https://git.openjdk.org/jdk/pull/13192