C'tors from templates

[dsimcha]

== Quote from Robert Clipsham (robert at octarineparrot.com)'s article
> dsimcha wrote:
> > Is there a way to run a class's c'tor on a block of memory from a template
> > function?  For example:
> >
> > C newClass(C, CtorArgs...)(CtorArgs args) {
> >     // Allocate, initialize.
> >     // Want to call the c'tor that takes type CtorArgs.
> > }
> ----
> C newClass(C, CtorArgs...)(CtorArgs args) {
>      return new C(args);
> }
> class Foo{ this(int a, string b) { /* do something */ } }
> auto foo = newClass!(Foo)(1, "bar");
> ----
> That seems to work here... or are you meaning you already have a block
> of memory allocated and want to turn it into an instance of the class?
> In which case something like:
> ----
> C newClass(C, CtorArgs...)(CtorArgs args) {
>     void* mem;
>     // Allocate/initialize etc, store in inst of type C
>     // Stolen/adapted from Object.d:
>     if( inst.classinfo.flags & 8 && inst.classinfo.defaultConstructor )
>     {
>         C delegate(CtorArgs) ctor;
>         ctor.ptr = cast(void*)inst;
>         ctor.funcptr = cast(C function(CtorArgs))
>                            inst.classinfo.defaultConstructor;
>         return ctor(args);
>     }
>     return null;
> }
> ----
> Should work (untested).

I meant the latter, but not just for the default constructor, for any constructor.