Integrated: 8317048: VerifyError with unnamed pattern variable and more than one components

[Aggelos Biboudis]

On Fri, 29 Sep 2023 10:20:10 GMT, Aggelos Biboudis <abimpoudis at openjdk.org> wrote:

> There were situations when javac optimizes switch structures (by merging the head of cases recursively) when two neighboring cases have a mix of named and unnamed patterns. This resulted translation is like the following:
> 
> From this:
> 
> 
>   static <T1 extends Comparable, T2 extends Comparable> int compareTo(Tuple<R<T1>, R<T2>> o) {
>         return switch (o) {
>             case Tuple<R<T1>, R<T2>>(R1<T1> _, R1<T2> _) -> -1;
>             case Tuple<R<T1>, R<T2>>(R1<T1> _, R2<T2> _) -> -1;
>             case Tuple<R<T1>, R<T2>>(R2<T1> _, R1<T2> _) -> -1;
>             case Tuple<R<T1>, R<T2>>(R2<T1> fst, R2<T2> snd) -> fst.value().compareTo(snd.value());
>         };
>     }
> 
> 
> to code like this from the deeper nested switch (sample taken from `translateTopLevelClass`):
> 
> 
> ...
> case 1:
>    if (!(let snd = (T8317048.R2)selector10$temp; in true)) {
>        index$11 = 2;
>        continue;
>    }
>    yield .value().compareTo(snd.value()); // boom, fst is missing
>    break;
> ...
> 
> 
> The reason is that in the `resolveAccumulator` we peek the first of the two to replace both, in this case the `R2<T1> _`. 
> 
> 
> JCPatternCaseLabel leadingTest = 
>         (JCPatternCaseLabel) accummulator.first().labels.head;
> 
> 
> One way to solve this is to not merge two successive type patterns that have different namings (either both named or both unnamed).

This pull request has now been integrated.

Changeset: 36de19d4
Author:    Aggelos Biboudis <abimpoudis at openjdk.org>
Committer: Jan Lahoda <jlahoda at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/36de19d4622e38b6c00644b0035521808574e255
Stats:     89 lines in 2 files changed: 89 ins; 0 del; 0 mod

8317048: VerifyError with unnamed pattern variable and more than one components

Reviewed-by: jlahoda

-------------

PR: https://git.openjdk.org/jdk/pull/15983