Is it valid if I call GC.addRange with same or overlaping range?
Example:

https://run.dlang.io/is/a5a0Ag

import core.memory;
import std.experimental.allocator.mallocator;
import core.lifetime;

class Bar{
}

struct Foo{
    Bar bar;

    this(Bar bar){
        this.bar = bar;
    }
}


void main(){
    void[] buffer = Mallocator.instance.allocate(Foo.sizeof * 10);
    scope(exit){
	GC.removeRange(buffer.ptr);
        Mallocator.instance.deallocate(buffer);
    }

    GC.addRange(buffer.ptr, Foo.sizeof);
    emplace(cast(Foo*)buffer.ptr, new Bar);

    GC.addRange(buffer.ptr, Foo.sizeof*2);  //Overlaps previous range, is it OK?
    emplace(cast(Foo*)(buffer.ptr + Foo.sizeof), new Bar);
}