I understand, but the trampolines cause bloat, and if you're
suggesting treating all non-JsFunction Java8 lambdas as JsFunctions as
far as code-gen is concerned, then you would not be able to make the
following code work:
foo(Callable x) { bar(x); }
foo(Runnable x) { bar(x); }
bar(Object x) { if (x instanceof Callable) { print("it's a callable");
} else if (x instanceof Runnable) { print("It's a runnable"); } }
You need a castMap for that.
On Mon, Apr 18, 2016 at 10:17 AM, 'Roberto Lublinerman' via GWT
Contributors <google-web-toolkit-contributors@googlegroups.com> wrote:
> The point is that for JsFunctions you DON'T actually need to do the
> makeLambda(). JsFunction was designed to be able to pass JS functions to
> JAVA so there is a code path for that and we can exploit it for JsFunction
> lambdas.
>
> So x -> 42 + capture will be represented in the JAva AST as
> class X {
> {
> ..... new X$0(capture);
> }
> // Synthetic lambda method
> int lambda_f(capture, x) {
> return 42 + capture;
> }
>
> // Lambda function implmenetation. Nothing needs to be emitted for this in
> JS
> class X$0 implements JsFunctionInterface {
> capture;
> X$0(capture) {
> this.capture = capture;
> }
>
> int m(x) {
> X.lambda_f(this.capture, x);
> }
> }
>
>
> In the JS ast we do
>
> new X$0(capture) --> function(x) { X.lambda_f(capture, x) }
>
> So we don't need makeLambda or anything else; we can just treat JsFunciton
> implementation as if they were functions passed in from JavaScript where
> object methods will go through the regular trampoline into the "JSO"
> implementation.
>
>
>
>
> On Mon, Apr 18, 2016 at 9:55 AM, 'Ray Cromwell' via GWT Contributors
> <google-web-toolkit-contributors@googlegroups.com> wrote:
>>
>> That seems similar to my proposal, only you're doing it in GenJsAST.
>> You'll still need to the makeLambda() trick to allow it to work as a
>> regular obejct as well, with hashCode()/equals()/getClass()
>> properties, as well as castMap installed. But if you use static method
>> delegation, the size won't be as ideal if the static method doesn't
>> inline.
>>
>> You want something like x -> 42 + capture to compile to
>> makeLambda(function(x) { return 42 + capture }, castMap, classLit),
>> not function(x) { return Class.foo(capture, x); } do you not?
>>
>>
>> On Mon, Apr 18, 2016 at 9:49 AM, 'Roberto Lublinerman' via GWT
>> Contributors <google-web-toolkit-contributors@googlegroups.com> wrote:
>> > The scheme I had in mind does not modify much the Java AST
>> > representation
>> > but is more in the lowering to the JsAST, basically it boils down the
>> > the
>> > following:.
>> > 1. You create the lambda body as a static method of the class where it
>> > appears. This static method has all captures as parameters (thiis is
>> > very
>> > similar as we are doing today).
>> > 2. Synthesize an anonymous inner class that implement the JsFunciton
>> > (also
>> > same as we are doing now). The compiler in the java phase sees this as
>> > an
>> > innerclass.
>> > 3. Emit the following code for new JsFuncitonimplementation(capture1,
>> > capture2) as function(par1, par2, parn) ->
>> > {Class.lambdaFunctionImplementation(capture1, capture2, par1, par2,
>> > parn) }.
>> > 4. Do not emit any code for the anonymous inner class.
>> >
>> > This function will behave as if it was a native function passed from JS,
>> > and
>> > object methods will work in the same way. Of course the devil is in the
>> > details.
>> >
>> >
>> > On Mon, Apr 18, 2016 at 9:34 AM, 'Ray Cromwell' via GWT Contributors
>> > <google-web-toolkit-contributors@googlegroups.com> wrote:
>> >>
>> >> Seems to me this'll be tricky to pull off. The GWT compiler has no
>> >> notion of captured scope. If you want to create a class type that
>> >> represents a lambda, but which doesn't actually get output as a class,
>> >> you'd have to change many many parts of the compiler.
>> >>
>> >> I think perhaps the best thing you could do would be a kind of
>> >> 'peephole' optimization pass. After all Java optimization passes have
>> >> run, and after JS has been generated, go through using pattern
>> >> matching to find "new generatedlambda(captured variables)" and replace
>> >> it with "makeLambda(classtype, castMap, classLiteral, function(...) {
>> >> body of single abstract method })". Then hope the JS dead code pruning
>> >> removes the unused inner class.
>> >>
>> >> I think if you try to model this in the Java AST it would impact too
>> >> much
>> >> stuff.
>> >>
>> >>
>> >> On Mon, Apr 18, 2016 at 9:04 AM, 'Roberto Lublinerman' via GWT
>> >> Contributors <google-web-toolkit-contributors@googlegroups.com> wrote:
>> >> > We accept patches :)
>> >> >
>> >> > On Sun, Apr 17, 2016 at 8:40 PM, Paul Stockley <pstockl...@gmail.com>
>> >> > wrote:
>> >> >>
>> >> >> Given that it will be realistically a couple of years before most
>> >> >> large
>> >> >> projects could migrate to J2CL, it would be really nice to have a
>> >> >> more
>> >> >> optimal code generation for lambda's, especially for JsFunction.
>> >> >> When
>> >> >> 2.8
>> >> >> gets released, I think people will really start taking advantage of
>> >> >> existing
>> >> >> JS libraries that really heavily use functions.
>> >> >>
>> >> >>
>> >> >> On Friday, April 15, 2016 at 12:03:12 PM UTC-4, Roberto Lublinerman
>> >> >> wrote:
>> >> >>>
>> >> >>> It should not be hard to make JsFunction lambdas more terse, but
>> >> >>> there
>> >> >>> are no plans for GWT 2.x.
>> >> >>>
>> >> >>>
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