Anyway to achieve the following

[JG]

On Saturday, 14 August 2021 at 20:50:47 UTC, Carl Sturtivant 
wrote:
> ```
> struct S {
>   int x = 1234;
> }
>
> void main() {
>   import std.stdio;
>    S s;
>    //construction of a using &(s.x)
>    auto a = Ref!(int)(&s.x);
>    writeln(a); //displays 1234
>    s.x += 1;
>    writeln(a); //displays 1235
>    a += 1;
>    writeln(s.x); //displays 1236
> }
>
> struct Ref(T) {
>   T* ptr;
>   this(T* p) { ptr = p; }
>   string toString() { import std.conv; return to!string(*ptr); }
>   ref T var() { return *ptr; }
>   alias var this;
> }
> ```

Hi,

This is exactly the behaviour I was trying to obtain.

It however comes with a fair amount of overhead, as can be seen 
in the following llvm ir:

     define i32 @_Dmain({ i64, { i64, i8* }* } %unnamed) #0 {
       %s = alloca %onlineapp.S, align 4               ; [#uses = 
4, size/byte = 4]
       %a = alloca %"onlineapp.Ref!int.Ref", align 8   ; [#uses = 
5, size/byte = 8]
       %1 = bitcast %onlineapp.S* %s to i8*            ; [#uses = 
1]
       call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 1 %1, i8* 
align 1 bitcast (%onlineapp.S* @onlineapp.S.__init to i8*), i64 
4, i1 false)
       %2 = bitcast %"onlineapp.Ref!int.Ref"* %a to i8* ; [#uses = 
1]
       call void @llvm.memset.p0i8.i64(i8* align 1 %2, i8 0, i64 
8, i1 false)
       %3 = getelementptr inbounds %onlineapp.S, %onlineapp.S* %s, 
i32 0, i32 0 ; [#uses = 1, type = i32*]
       %4 = call %"onlineapp.Ref!int.Ref"* @pure nothrow ref @nogc 
@safe onlineapp.Ref!(int).Ref 
onlineapp.Ref!(int).Ref.__ctor(int*)(%"onlineapp.Ref!int.Ref"* 
nonnull returned %a, i32* %3) #4 ; [#uses = 0]
       %5 = load %"onlineapp.Ref!int.Ref", 
%"onlineapp.Ref!int.Ref"* %a, align 8 ; [#uses = 1]
       call void @@safe void 
std.stdio.writeln!(onlineapp.Ref!(int).Ref).writeln(onlineapp.Ref!(int).Ref)(%"onlineapp.Ref!int.Ref" %5) #4
       %6 = getelementptr inbounds %onlineapp.S, %onlineapp.S* %s, 
i32 0, i32 0 ; [#uses = 2, type = i32*]
       %7 = load i32, i32* %6, align 4                 ; [#uses = 
1]
       %8 = add i32 %7, 1                              ; [#uses = 
1]
       store i32 %8, i32* %6, align 4
       %9 = load %"onlineapp.Ref!int.Ref", 
%"onlineapp.Ref!int.Ref"* %a, align 8 ; [#uses = 1]
       call void @@safe void 
std.stdio.writeln!(onlineapp.Ref!(int).Ref).writeln(onlineapp.Ref!(int).Ref)(%"onlineapp.Ref!int.Ref" %9) #4
       %10 = call i32* @pure nothrow ref @nogc @safe int 
onlineapp.Ref!(int).Ref.var()(%"onlineapp.Ref!int.Ref"* nonnull 
%a) #4 ; [#uses = 2]
       %11 = load i32, i32* %10, align 4               ; [#uses = 
1]
       %12 = add i32 %11, 1                            ; [#uses = 
1]
       store i32 %12, i32* %10, align 4
       %13 = getelementptr inbounds %onlineapp.S, %onlineapp.S* 
%s, i32 0, i32 0 ; [#uses = 1, type = i32*]
       %14 = load i32, i32* %13, align 4               ; [#uses = 
1]
       call void @@safe void 
std.stdio.writeln!(int).writeln(int)(i32 %14) #4
       ret i32 0
     }