Assigning a scope variable to an outer-scope variable is allowed?

["のしいか (noshiika)"]

Hello. I have a question about "scope" variables.

I've understood that it is not allowed to copy a scope variable or a 
scope parameter to outside of the scope. But, the following code 
compiles without any warnings or errors, and of course, causes a runtime 
error.

Is this just a bug?

//----

class C {
     ~this() { writefln("dtor"); }
     void func() { }
}
void main() {
     C a;
     {   scope C b = new C;
         a = b;
     } // dtor
     if(a !is null) a.func(); // Error: Access Violation
}

const(int[]) g;
void foo(in int[] a) { // in == final const scope
     g = a;  // a is scope?
}