Question about scope

[Nemanja Boric via Digitalmars-d]

Taken from 
https://github.com/dlang/druntime/pull/1750#discussion_r98181564:

```
void bar(scope char** c, scope int* n) @trusted
{
}

void foo() @safe
{
     char[100] buf;
     char* c = &buf[0];
     int n;

     bar(&c, &n);
}

void main()
{
     foo();
}
```

This doesn't compile even with dip1000, but does compile when 
`buf` is moved out of the scope. Can somebody explain why it 
fails and what needs to be done with it?