Refactor object.d: Move __ArrayCast to rt - #2643

Is putting each function in a separate file the direction this is going? One file for __equals, one file for __ArrayCast?

Is putting each function in a separate file the direction this is going?

No. The idea is to leverage modules and packages as D's unit of encapsulation. Those functions/features/etc. that don't depend on each other should go into their own module.

When I attempt to move dup, __dopostblit, _trustedDup, etc., those would go together in one module, because there is a dependency between them.

Edit: It may turn out that there will basically be one public runtime hook per file, but that is not the motivation. The motivation is encapsulation.

Thanks for your pull request and interest in making D better, @JinShil! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
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