Comparators.comparing inference error

[Brian Goetz]

Yes, this is being worked on.

On 4/18/2013 2:18 PM, Michael Nascimento wrote:
> Hi folks,
>
> I had a comparison chain in Guava which I tried to migrate by creating
> a comparator:
>
> Comparator<YearMonthDecade> c = Comparators
> .comparing(YearMonthDecade::getYearMonth)
> .thenComparing(YearMonthDecade::getDecadeNumber);
>
> getYearMonth returns a YearMonth and getDecadeNumber returns an int. I
> get the following compiler error:
>
> YearMonthDecade.java:[69,4] error: reference to comparing is ambiguous
>    both method <T#1>comparing(ToLongFunction<? super T#1>) in
> Comparators and method <T#2>comparing(ToDoubleFunction<? super T#2>)
> in Comparators match
>    where T#1,T#2 are type-variables:
>      T#1 extends Object declared in method
> <T#1>comparing(ToLongFunction<? super T#1>)
>      T#2 extends Object declared in method
> <T#2>comparing(ToDoubleFunction<? super T#2>)
> YearMonthDecade.java:[69,14] error: incompatible types: Cannot
> instantiate inference variables T because of an inference loop
>
> I can get it to compile with:
>
> Comparator<YearMonthDecade> c = Comparators
> .<YearMonthDecade,YearMonth>comparing(YearMonthDecade::getYearMonth)
> .<YearMonthDecade>thenComparing((ToIntFunction<YearMonthDecade>)
> YearMonthDecade::getDecadeNumber);
>
> Do you plan to make this work somehow (smarter compiler or no
> overloading anymore)?
>
> Regards,
> Michael
>