RFR: 8174222: LambdaMetafactory: validate inputs and improve documentation [v2]

[Dan Smith]

On Fri, 4 Jun 2021 01:22:05 GMT, liach <github.com+7806504+liach at openjdk.org> wrote:

>> Dan Smith has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix accidentally commented-out parts of test
>
> src/java.base/share/classes/java/lang/invoke/LambdaMetafactory.java line 547:
> 
>> 545:             throw new IllegalArgumentException("argument has wrong type");
>> 546:         }
>> 547:         return type.cast(result);
> 
> Can we just use a `return (T) result` as there will always be a checked cast on the caller's end, and this call seems redundant? The only shortcoming is that the call will raise an unchecked warning that needs to be suppressed. Or is this negligible after hotspot optimization?

Eh, the scale here is quite small (never more than, say, 20 items), and an instanceof + a cast is a routine coding style that I'd expect to be optimized away. Doesn't seem worth the maintenance noise of a `@SuppressWarnings`.

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PR: https://git.openjdk.java.net/jdk/pull/4346