Java type annotations, multi-precision

[bearophile]

Walter Bright:

> Much like how ROR and ROL is efficiently handled in compilers 
> by having the compiler recognize the equivalent expression, I 
> think the best way to handle these issues is by having the 
> compiler recognize the multi-precision expressions, and rewrite 
> it internally into the optimal asm.

See:
https://d.puremagic.com/issues/show_bug.cgi?id=6829

My opinions:
- It's a fragile pattern recognition. In D.learn and elsewhere I 
have seen people write the rot/rol in a way that DMD is not able 
to recognize.
- It's not portable, because there is no guarantee that other 
present or future compilers will perform that optimization. See 
that issue 6829 thread for problems with LLVM.
- Generally it's nice to have a language that offers higher level 
operations to the programmer, making coding simpler. But in this 
case calling a function as rol/ror is very easy for the 
programmer, it is not a burden at all. Replacing it with a 
pattern to be written carefully is not a gain for the programmer. 
And it helps the person that later reads the code at a bit higher 
level (and currently Phobos doesn't have such ror/rol functions, 
so they need to be written in user code).

Here I have suggested something different:
https://d.puremagic.com/issues/show_bug.cgi?id=9850

Bye,
bearophile