Debug help - opDispatch - unknown member function

[Brother Bill]

On Tuesday, 9 September 2025 at 09:59:40 UTC, Dejan Lekic wrote:
>
> Hopefully this slightly modified, and commented version of your 
> original code will
> help you understand why your mixin is failing:
>
> ```d
> import std.stdio;
>
> void main() {
>     CallLogger!C l;
>     l.callA(1, 2);
>     l.callB("ABC");
>
>     // CallLogger does not have method called "callHome", but 
> it has opDispatch, so
>     // the compiler will lower this down to 
> l.opDispatch("callHome", "foo", "bar")
>     l.callHome("foo", "bar");
> }
>
> struct C {
>     void callA(int i, int j) {
>     }
>
>     void callB(string s) {
>     }
>
>     // Your mixin generates code that calls C.callHome which 
> did not exist
>     void callHome(string a, string b) {
>         writeln(a, "/", b);
>     }
> }
>
> struct CallLogger(C) {
>     C content;
>     void opDispatch(string name, T...)(T vals) {
>         writeln("called ", name);
>
>         // Now it works, because C now has callHome method
>         mixin("content." ~ name)(vals);
>     }
> }
> ```

When commenting out the callHome() in struct C, it fails.
Obviously if callHome() is explicitly created, it works.

```
import std.stdio;

void main() {
     CallLogger!C l;
     l.callA(1, 2);
     l.callB("ABC");

     // CallLogger does not have method called "callHome", but it 
has opDispatch, so
     // the compiler will lower this down to 
l.opDispatch("callHome", "foo", "bar")
     l.callHome("foo", "bar");
}

struct C {
     void callA(int i, int j) {
     }

     void callB(string s) {
     }

     // Your mixin generates code that calls C.callHome which did 
not exist
     // void callHome(string a, string b) {
     //     writeln(a, "/", b);
     // }
}

struct CallLogger(C) {
     C content;
     void opDispatch(string name, T...)(T vals) {
         writeln("called ", name);

         // Now it works, because C now has callHome method
         mixin("content." ~ name)(vals);
     }
}
```

Console contents:
```
c:\dev\D\D_templates_tutorial\toy1\source\app.d(10): Error: no 
property `callHome` for `l` of type `app.CallLogger!(C)`
     l.callHome("foo", "bar");
      ^
```