import std.experimental.all;

​

auto assumePure(T)(T t)

if (isFunctionPointer!T || isDelegate!T)

{

    enum attrs = functionAttributes!T | FunctionAttribute.pure_;

    return cast(SetFunctionAttributes!(T, functionLinkage!T, attrs)) t;

}

​

struct A

{   

​

    @disable this();

    this(size_t i) { ctors++; this.i = i; writeln("CTOR ", i); }

    ~this() { dtors++; writeln("DTOR ", i); }

    void dbg() { ctors++;  writeln("POSTBLIT ", i); }

    pure this(this) 

    { 

        assumePure(&dbg)(); 

    }

    static size_t ctors = 0;

    static size_t dtors = 0;

    size_t i;

}

​

​

struct Range

{

    //@property size_t length = 4;  // Uncomment this line for a similar result!

    @property A front() { return A(count); }

    void popFront() { count++; }

    @property empty() { return count > 3; }

    size_t count = 0;

}

​

void main()

{

    // This is never freed, apparently

    {

        auto tmp = Range();

        tmp.array.writeln;

    }

    import core.memory;

    GC.collect();

}

​

static ~this() 

{ 

    writeln(A.ctors, "ctors vs ", A.dtors, " dtors"); 

}