• vit (36/36) Mar 12 2022 Hello,
• Salih Dincer (18/21) Mar 12 2022 I think you meant build instead of touch?

vit <vit vit.vit> writes:

Hello,
why this code compile without problems:

```d

struct Query{
     public const SharedPtr!Builder builder;
}

interface Builder{
     void build(ref Query query);
}

struct SharedPtr(T){
     enum touch_T = __traits(hasMember, T, "touch");
     //...
}


void main(){

}

```

but if `ref Query query` is scope then there is error?

```d

struct Query{
     public const SharedPtr!Builder builder;
}

interface Builder{
     void build(scope ref Query query);     //SCOPE
}

struct SharedPtr(T){
     enum touch_T = __traits(hasMember, T, "touch");
     //...
}



void main(){

}
```

```
src/app.d(3,1): Error: no size because of forward references
src/app.d(4,18): Error: template instance 
`app.SharedPtr!(Builder)` error instantiating

```

Salih Dincer <salihdb hotmail.com> writes:

On Saturday, 12 March 2022 at 13:12:25 UTC, vit wrote:
 ```d
 enum touch_T = __traits(hasMember, T, "touch");
 ```

I think you meant build instead of touch?

```d
struct Query {
   public const SharedPtr!Builder builder;
}

interface Builder {
   void build(ref Query query);
}

struct SharedPtr(T) {
     enum touch_T = __traits(hasMember, T, "build");
}

import std.traits, std.stdio;

void main() {
   Query q;
   q.builder.touch_T.writeln(" #build");
} // true #build
```