Leak-detection of references to scoped class instances

[Per Nordlöw]

Why doesn't DMD detect invalid out-of-scope references to scoped 
class instances?

Example:

@safe:

class C
{
@safe pure:
     this()
     {
     }
     int x;
}

@trusted unittest
{
     C f()
     {
         import std.typecons : scoped;
         auto x = scoped!C();
         return x;
     }
     auto c = f();
     c.x = 42;                   // invalid memory access
}