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/jdk.compiler/share/classes/com/sun/tools/javac/comp/Attr.java line 201:

> 199:     /** Are unconditional patterns in instanceof allowed
> 200:      */
> 201:     private boolean allowUnconditionalPatternsInstanceOf;

so I guess this field can be made final now

src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Flow.java line 909:

> 907: 
> 908:                             Set<Symbol> permitted = allPermittedSubTypes(clazz, csym -> {
> 909:                                 Type instantiated = infer.instantiatePatternType(selectorType, csym);

for some cases, when there are no type parameters, this invocation is a no-op, do we really need inference at this point?

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PR Review Comment: https://git.openjdk.org/jdk/pull/13074#discussion_r1171830887
PR Review Comment: https://git.openjdk.org/jdk/pull/13074#discussion_r1171936405