On Thu, 20 Apr 2023 13:41:05 GMT, Jan Lahoda <jlah...@openjdk.org> wrote:
>> 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 {
>>
>> out of curiosity, under what conditions the `startIndex` would be different
>> from `0`? also shouldn't we check that `startIndex` is `>= 0`?
>
> `startIndex` may be non-0 when there are guards in the switch. In the case of
> the `enumSwitch`, something like:
>
> enum E {A, B;}
> E e = E.B;
> switch (e) {
> case E ee when ee == E.A -> {}
> case E ee -> {}
> }
>
>
> the method will be called twice, one with `startIndex == 0` and once with
> `startIndex == 1`, after the guard fails/returns `false`.
I see, thanks
>> 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;
>> }
>>
>> EDIT: nvm I found one example
>
> The intent here is to avoid eager initialization of enums - so, until the
> enum is initialized, `lazyDoEnumSwitch` will be used (which, by itself, won't
> compute any results, except the result for `null`), which is then replaced
> with `doEnumSwitch` using the enum constants directly.
>
> The enum switches support patterns as well, so something like:
>
> enum E {A;}
> E e = ...;
> switch (e) {
> case E ee -> {}
> }
>
> is valid, and should trigger the part with Class labels.
yep I found a similar test case triggering this code
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/13074#discussion_r1172646957
PR Review Comment: https://git.openjdk.org/jdk/pull/13074#discussion_r1172647746
