refInt = ref int: how to achieve this? or is this a bug?

[Avrina]

On Wednesday, 17 June 2020 at 21:27:01 UTC, mw wrote:
> On Wednesday, 17 June 2020 at 20:47:59 UTC, Steven 
> Schveighoffer wrote:
>> Essentially, your alias statement becomes:
>>
>> alias refInt = int;
>>
>> Which in itself is somewhat of a "feature", as storage classes 
>> that do not apply are ignored. Some may consider it a bug, but 
>> I haven't seen anyone attempt something like what you have, it 
>> sure seems like the compiler should complain.
>
> I would consider it a bug, *even* C++ can handle this better 
> :-)  i.e. no surprise to the programmer.
>
> cat reft.cpp
> ----------------------
> #include <stdio.h>
>
> typedef int& refInt;
>
> void f(refInt i) {
>   i = 456;
> }
>
> int main() {
>   int i = 123;
>   printf("%d\n", i);
>   f(i);
>   printf("%d\n", i);
> }
> ----------------------
>
> $ make reft
> g++     reft.cpp   -o reft
>
>
> $ ./reft
> 123
> 456

It's not a bug, it is purposefully designed to be that way.

Just like you can't do ref variables.


void main() {
    int a;
    int& b = a; // ok C++
    ref int c = a; // not valid D
}


You can do something like this instead, not sure what you are 
trying to do tho. Could just be easier to put a separate function 
in the `static if` that you are trying to define the ref type in 
instead.


import std.stdio;

void foo(T)(auto ref T v) if (is(T : int) == __traits(isRef, v)) {
     writeln(__traits(isRef, v) ? "by ref" : "by value");
}

void main() {
	int a;
     foo(a); // by ref
     // foo(10); // error by value

     float b;
     // foo(b); // error by ref
     foo(10.0f); // by value
}