Continuation passing style vs. wrapper objects in dmd

[Andrei Alexandrescu]

dmd has a few string functions with names having "Then" as a prefix that 
take a lambda and call it with a temporary string converted for OS 
purposes (zero-terminated, encoded a specific way etc). The use goes 
like this:

int i = module_name.toCStringThen!(name => stat(name.ptr, &statbuf));

The way it goes, `module_name` gets converted from `char[]` to 
null-terminated `char*`, the lambda gets invoked, then whatever 
temporary memory allocated is freed just after the lambda returns.

I was thinking there's an easier way that's also more composable:

int i = stat(stringz(name).ptr, &statbuf));

where `stringz` returns a temporary struct offering primitives such as 
`ptr` and `opSlice`. In the destructor, the struct frees temporary 
memory if allocated. Better yet, it can return them as `scope` variable, 
that way ensuring correctness in safe code.

Destruction of temporary objects has been sketchy in the past but I 
assume things have been ironed out by now.