Declaring rvalue function arguments

[Matt Elkins via Digitalmars-d-learn]

On Sunday, 31 January 2016 at 18:02:19 UTC, Matt Elkins wrote:
> Here is the one I am using right now:

Actually, here is the whole module in case you are interested in 
the unittests/usage:

[code]
import std.algorithm;
import std.traits;

struct ResourceHandle(T, alias Deleter, T Default = T.init)
{
     // Constructors/Destructor
     this(in T handle) {m_handle = handle;}
     @disable this(this);
     ~this() {Deleter(m_handle);}

     // Operators
     @disable void opAssign(ref ResourceHandle lvalue);
     ref ResourceHandle opAssign(ResourceHandle rvalue) 
{swap(m_handle, rvalue.m_handle); return this;}

     // Methods
     @property T handle() const {return m_handle;}
     @property T handle(T handle) {Deleter(m_handle); m_handle = 
handle; return m_handle;}
     T release() {T result = m_handle; m_handle = Default; return 
result;}

     private:
         T m_handle = Default;
}

@nogc @safe nothrow unittest
{
     static uint destroyedCount;
     static uint lastDestroyed;
     alias RH = ResourceHandle!(uint, (uint resource){if (resource 
!= uint.init) {lastDestroyed = resource; ++destroyedCount;}});

     // Test basic resource cleanup
     assert(destroyedCount == 0);
     assert(lastDestroyed != 7);
     {auto handle0 = RH(7);}
     assert(destroyedCount == 1);
     assert(lastDestroyed == 7);

     // Test releasing
     {
         auto handle0 = RH(8);
         assert(handle0.handle == 8);
         assert(handle0.release() == 8);
         assert(handle0.handle == uint.init);
         assert(destroyedCount == 1);
         assert(lastDestroyed == 7);
     }
     assert(destroyedCount == 1);
     assert(lastDestroyed == 7);

     {
         // Test that copying and lvalue assignment are disabled
         auto handle0 = RH(5);
         static assert (!__traits(compiles, {auto handle1 = 
handle0;}));
         static assert (!__traits(compiles, {RH handle1; handle1 = 
handle0;}));

         // Test that rvalue assignment works
         auto makeRH(uint value) {return RH(value);}
         handle0 = makeRH(3);
         assert(destroyedCount == 2);
         assert(lastDestroyed == 5);
     }
     assert(destroyedCount == 3);
     assert(lastDestroyed == 3);

     // Test setting in static array
     {
         RH[3] handles;
         handles[0] = RH(9);
         assert(destroyedCount == 3);
         assert(lastDestroyed == 3);
     }
     assert(destroyedCount == 4);
     assert(lastDestroyed == 9);

     // Test setting to resource directly
     {
         auto handle0 = RH(11);
         assert(destroyedCount == 4);
         assert(lastDestroyed == 9);
         assert(handle0.handle == 11);
         handle0.handle = 12;
         assert(destroyedCount == 5);
         assert(lastDestroyed == 11);
         assert(handle0.handle == 12);
     }
     assert(destroyedCount == 6);
     assert(lastDestroyed == 12);
}
[/code]