search of a workaround

[Namespace]

I've been thinking about the lack of rvalue references. 
Therefore, I would like to know what you think is the best 
workaround for this feature.
I illustrate below the only (*) five solutions briefly and 
summarized.
What do you think is the best? Which of these do you use? Or did 
I forget some possible solutions?
I'm looking for this for small data structures, such as vectors, 
matrices, or colors.

(*) In my opinion.

--------

struct A { }

  ---- Solution #1 ----

// rvalues
void foo(A a) {
	foo(a);
}

// lvalues
void foo(ref A a) {

}

----------------------------------
Summarized: flexible, efficient but code bloat, more effort and 
bug prone:

void foo(A a) {
	writeln("call no ref");
	foo(a);
}

void foo(const ref A a) {
	writeln("call ref");
}

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

-> endless loop!

  ---- Solution #2 ----

// fuck it, copy lvalues and rvalues
void foo(A a) {

}

----------------------------------
Summarized: flexible, no code bloat but inefficient -> 
unnecessary copies

  ---- Solution #3 ----

// allow only lvalues
void foo(ref A a) {

}

----------------------------------
Summarized: You have to make temporary values by yourself: 
unhandy, ugly and code bloat

  ---- Solution #4 ----

// accept only pointers
void foo(A* a) {

}

----------------------------------
Summarized: C Style, nullable and same problems as with solutions 
#3.

  ---- Solution #5 ----

// Use classes
class A { }

// Works for lvalues and rvalues
void foo(A a) {

}

----------------------------------
Summarized: flexible, efficient, no code bloat and same creation 
(with static opCall) as structs. But: heap allocations and 
nullable.