I can has @nogc and throw Exceptions?

[Jonathan Marler via Digitalmars-d-learn]

This question comes from wanting to be able to throw an exception 
in code that is @nogc.

I don't know if it's possible but I'd like to be able to throw an 
exception without allocating memory for the garbage collector?  
You can do it in C++ so I think you should be able to in D.  One 
idea I had was to allocate the memory for the Exception 
beforehand and create the Exception class with the pre-allocated 
memory.  I came up with the following code:

T construct(T,A...)(void* buffer, A args)
{
   return (cast(T)buffer).__ctor(args);
}

Now to test it:

void main()
{
   ubyte[ __traits(classInstanceSize, Exception)] exceptionBuffer;
   throw construct!(Exception)(exceptionBuffer.ptr, "My Exception 
Allocated on the STACK!");
}

I got an assertion error. I'm not sure why, but when I print out 
the contents of the buffer of my stack exception it differs from 
an exception created for the garbage collector with "new".  It 
looks like it has some accounting information embedded in the 
class instance. I figured as much but I didn't think the code 
that performs the "throw" would be dependent on this.

Also, this doesn't look like a very safe option because the 
initial values for the class members don't get set using this 
"construct" template.

If anyone has any other ideas or a way to fix mine let me know, 
thanks.