RFR: 8276789: Support C++ lambda in ResourceHashtable::iterate [v4]

[Ioi Lam]

On Thu, 2 Jun 2022 05:10:05 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> [Not a review, just a drive-by comment]
>> SFINAE operates on arguments and signatures; it doesn't reach into the bodies
>> of (potential) callees like that. The disambiguation is happening because one
>> argument (the Closure object) is passed as a pointer, while the other is a
>> lambda object (not a pointer). In the pointer to closure object case the ITER*
>> overload is a better match, so is selected. In the lambda case, it's not a
>> pointer so only the non-pointer overload is applicable.
>
> (And SFINAE _can't_ reach into the body like that, since the body might not be available.)

@kimbarrett Thanks for the explanation. So we're lucky because we use `ITER*` in the old API. If it were `ITER&` then the C++ compiler would complain about ambiguous overloading.

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PR: https://git.openjdk.java.net/jdk/pull/8761