D needs emplacement new

[Namespace via Digitalmars-d]

Consider both of these scripts: test_gc_new.d 
(http://dpaste.dzfl.pl/4f36b165c502) and test_gc_emplace_new.d 
(http://dpaste.dzfl.pl/ff4e3c35479f)

and these results:

test_gc_new:

>test_gc_new.exe "--DRT-gcopt=profile:1"
         Number of collections:  140
         Total GC prep time:  0 milliseconds
         Total mark time:  5 milliseconds
         Total sweep time:  9 milliseconds
         Total page recovery time:  2 milliseconds
         Max Pause Time:  0 milliseconds
         Grand total GC time:  18 milliseconds
GC summary:    5 MB,  140 GC   18 ms, Pauses    6 ms <    0 ms


test_gc_emplace_new:

>test_gc_emplace_new.exe "--DRT-gcopt=profile:1"
         Number of collections:  2
         Total GC prep time:  0 milliseconds
         Total mark time:  0 milliseconds
         Total sweep time:  0 milliseconds
         Total page recovery time:  0 milliseconds
         Max Pause Time:  0 milliseconds
         Grand total GC time:  0 milliseconds
GC summary:    5 MB,    2 GC    0 ms, Pauses    0 ms <    0 ms

As you can see, thanks to the emplacement, I have 138 less GC 
collections. In C++ you can do

new (f) Foo(...) instead of my New!(Foo)(f, ...)

The C++ version is a lot more readable, nicer and safer. 
Therefore D should (since it says it is a system language like 
C++) add an equal syntax or, at least, implement a library 
version like mine to allow people a nice and easy way to reuse 
their object. We already have emplace (which my implementation 
uses) but to write emplace((cast(void*) obj)[0 .. 
__traits(classInstanceSize, Foo)], ...) is not nice, not 
intuitive and not safe and can be improved.