Allocating a wstring on the stack (no GC)?

[Maxime Chevalier-Boisvert via Digitalmars-d]

I have a very specific use case (JIT compiler) in which I have a 
pre-allocated array of wchar string data stored somewhere in 
memory. I'd like to be able to create a temporary D wstring 
object to pass this as a "regular" string to other functions. For 
performance reasons, it would be preferable not to dynamically 
allocate or copy any data. Dynamically allocating the strings 
tends to trigger the D GC which severely impacts the performance.

So, my question is, would it be possible for me to allocate a 
wstring object on the stack, and manually set its string data 
pointer and length? If so, how? Your wizardly help is much 
appreciated.