RFR: 8300543 Compiler Implementation for Pattern Matching for switch [v2]

[Vicente Romero]

On Tue, 18 Apr 2023 09:13:01 GMT, Jan Lahoda <jlahoda at openjdk.org> wrote:

>> This is the first draft of a patch for JEP 440 and JEP 441. Changes included:
>> 
>>  - the pattern matching for switch and record patterns features are made final, together with updates to tests.
>>  - parenthesized patterns are removed.
>>  - qualified enum constants are supported for case labels.
>> 
>> This change herein also includes removal record patterns in for each loop, which may be split into a separate PR in the future.
>
> Jan Lahoda has updated the pull request incrementally with six additional commits since the last revision:
> 
>  - Fixing infinite loop where a binding pattern is replaced with a binding pattern for the same type.
>  - Reflecting review comments.
>  - Fixing exhaustiveness for unsealed supertype pattern.
>  - No need to enable features after error reported.
>  - SwitchBootstraps.typeSwitch should not initialize enum classes.
>  - A prototype of avoiding enum initialization.

src/java.base/share/classes/java/lang/runtime/SwitchBootstraps.java line 279:

> 277:     }
> 278: 
> 279:     private static int lazyDoEnumSwitch(Enum<?> target, int startIndex, Object[] labels, MethodHandles.Lookup lookup, Class<?> enumClass, MutableCallSite callSite) throws Throwable {

can `doEnumSwitch` be folded into `lazyDoEnumSwitch`? just a suggestion, I'm OK with either way just that now it is not clear that we need two methods here. Also in `doEnumSwitch` and out of curiosity what example of user code could hit this section:


            if (label instanceof Class<?> c) {
                if (c.isAssignableFrom(targetClass))
                    return i;
            }

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PR Review Comment: https://git.openjdk.org/jdk/pull/13074#discussion_r1171605248