On Tue, 27 Oct 2020 10:40:40 GMT, Jorn Vernee <jver...@openjdk.org> wrote:
>>> …`dropReturn` seemed like a good choice since we already have
>>> `dropArguments`. WRT changing to `MethodHandle::changeReturnType`...
>>
>> That's a very reasonable point. People might look for `dropRT` after they
>> find `dropAs`. And `MHs` is designed as a large-ish set of utility methods.
>>
>> I agree that adding `MH::changeRT` is a slippery slope; it tends to lift
>> more of the MT API onto MH, and it starts to put new stuff into the smaller
>> MH API; that was my bad.
>>
>> But (in the spirit of brainstorming, and agreeing with your present
>> proposal), I'll suggest a separate idea to think about. Use a HOFP API to
>> give easy access to the entire `MT` API all in one go, by reifying the
>> `MH.type` property as a temporary (lambda argument):
>>
>> MethodHandle mapType(MethodHandle mh, UnaryOperator<MethodType> fn) {
>> return mh.asType(fn.apply(mh.type()));
>> }
>>
>> This also suggests a possible argument transform utility, a sort of
>> mini-version of Charlie Nutter's MH builder API:
>>
>> MethodHandle mapArguments(MethodHandle mh,
>> UnaryOperator<List<ArgumentValue<?>>> fn) {
>> var args = mh.type().argumentList().stream().map(t -> makeArg(t)).asList();
>> args = fn.apply(args);
>> … do stuff to re-weave mh with the resulting argument transforms …
>> }
>> public sealed interface ArgumentValue<T> {
>> Class<T> type();
>> <U> ArgumentValue<U> asType(Class<U> newType);
>> … other stuff for pre-applying MHs …
>> }
>
> It's an interesting idea. It turns something like:
>
> target = target.asType(target.type().changeReturnType(void.class));
>
> Into
>
> target = target.asType(mt -> mt.changeReturnType(void.class));
>
> I.e. it removes the need to reference the target handle/type twice, which
> prevents them from potentially going out of sync (which seems more likely
> when you have multiple MethodTypes and MethodHandles flying around). Also, it
> feels unnecessary that, I have to re-specify `target`'s type as a base, when
> I'm asking `target` to change it's type. This also solves that.
CSR is now provisional. Please review:
https://bugs.openjdk.java.net/browse/JDK-8255398
Thanks.
-------------
PR: https://git.openjdk.java.net/jdk/pull/866
