More pure optimizations

[Brad Roberts]

Ary Borenszweig wrote:
> bearophile escribió:
>> Ary Borenszweig:
>>> What if a different thread modifies h in between the loop?
>>
>> "h" associative array as a thread-local?
> 
> but from the method's signature:
> 
> int foo(int[string] h)
> 
> you can't tell that h is thread-local or not. Is that what you mean?

In D2, with shared vs non-shared memory becoming explicit, non-shared const
parameters can become legal pure parameters.  Since non-const can implicitly
convert to const, as long as the assoc array is non-shared and the key is
non-shared, then ... all the pieces fall into place to allow assoc array's
opIndex to have a pure version.

Whee,
Brad