How to convert member function to free function?

[Andrey Zherikov]

On Friday, 18 September 2020 at 18:20:41 UTC, Andrey Zherikov 
wrote:
> How can I rewrite foo() function as a free-function that won't 
> cause struct copying?

I found solution:
========
struct S
{
     int i = -1;
     this(int n) {i=n;writeln(&this," ",i," 
",__PRETTY_FUNCTION__);}
     this(ref return scope inout S rhs) inout 
{i=rhs.i+1;writeln(&this," ",i," ",__PRETTY_FUNCTION__);}
     ~this() {writeln(&this," ",i," ",__PRETTY_FUNCTION__);}
     ref auto getRef() return
     {
	    writeln(&this," ",i," ",__PRETTY_FUNCTION__);
         return this;
     }
}

ref auto foo(return ref S s)
{
     writeln(&s," ",s.i," ",__PRETTY_FUNCTION__);
     return s;
}

void main()
{
     S(5).getRef().foo().foo().foo();
}
========

Output confirms that there is no copying happens:
========
7FFDE98BDDF0 5 S onlineapp.S.this(int n) ref
7FFDE98BDDF0 5 onlineapp.S.getRef() ref return
7FFDE98BDDF0 5 onlineapp.foo(return ref S s) ref @system
7FFDE98BDDF0 5 onlineapp.foo(return ref S s) ref @system
7FFDE98BDDF0 5 onlineapp.foo(return ref S s) ref @system
7FFDE98BDDF0 5 void onlineapp.S.~this()
========