RFR: 8362885: A more formal way to mark javac's Flags that belong to a specific Symbol type only [v3]

[Jan Lahoda]

On Mon, 28 Jul 2025 21:10:24 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Jan Lahoda has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Reverting runtime checks, as suggested.
>
> make/langtools/tools/flagsgenerator/FlagsGenerator.java line 84:
> 
>> 82:                                            .forEach(target -> target2FlagBit2Fields.computeIfAbsent(target, _ -> new HashMap<>())
>> 83:                                                                                    .computeIfAbsent(flagBit, _ -> new ArrayList<>())
>> 84:                                                                                    .add(flagName));
> 
> Instead of a dedicated loop to verify no overlaps, we can make the nested map `Map<Integer, String>` and fail fast whenever we detect a conflict, like:
> 
> var oldFlagName = target2FlagBit2Fields.computeIfAbsent(target, _ -> new HashMap<>()).put(flagBit, flagName);
> if (oldFlagName != null) {
>     // Fail fast code
> }
> 
> I personally don't see a reason to collect all conflicting fields for a flag if any of these conflicts already causes a failure.

Its unlikely to be common in the long run, but there may be conflicts among more than two fields. Reporting all at once (rather than reporting one conflict, and after resolving reporting another) seems nicer.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26452#discussion_r2266167613