Proposal to make "shared" (more) useful

[Arafel]

On 09/13/2018 05:16 PM, Kagamin wrote:
> struct Unshared(T)
> {
>      private T value;
>      T get() shared { return cast(T)value; }
>      alias get this;
>      void opAssign(T v) shared { value=cast(shared)v; }
> }
> 
> shared synchronized class A
> {
>      private Unshared!(int[]) a;
>      int[] f()
>      {
>          return a;
>      }
> }
> 

Doesn't work:

```
import std.datetime.systime;

struct Unshared(T)
{
     private T value;
     T get() shared { return cast(T)value; }
     alias get this;
     void opAssign(T v) shared { value=cast(shared)v; }
}

shared synchronized class A {
     private Unshared!SysTime t;

     this() {
         t = Clock.currTime;
     }
}

void main() {
     shared A a = new shared A;
}
```

Gives you:

onlineapp.d(6): Error: non-shared const method 
std.datetime.systime.SysTime.opCast!(SysTime).opCast is not callable 
using a shared mutable object
onlineapp.d(6):        Consider adding shared to 
std.datetime.systime.SysTime.opCast!(SysTime).opCast
onlineapp.d(8): Error: template std.datetime.systime.SysTime.opAssign 
cannot deduce function from argument types !()(shared(SysTime)) shared, 
candidates are:
/dlang/dmd/linux/bin64/../../src/phobos/std/datetime/systime.d(612): 
    std.datetime.systime.SysTime.opAssign()(auto ref const(SysTime) rhs)
onlineapp.d(12): Error: template instance `onlineapp.Unshared!(SysTime)` 
error instantiating