mixin template

[vit]

On Monday, 23 May 2022 at 15:14:53 UTC, Vindex wrote:
> I have this code:
>
> ```
> import std.array, std.exception, std.stdio;
>
> mixin template RealizeException() {
>     this(string msg, string file = __FILE__, size_t line = 
> __LINE__) {
>         super(msg, file, line);
>     }
> }
>
> class WrongUsage : Exception {
>     mixin RealizeException;
>
>     this(string[] messages, string file = __FILE__, size_t line 
> = __LINE__) {
>         auto msg = std.array.join(messages, "\n");
>         super(msg, file, line);
>     }
> }
>
> void main() {
>     throw new WrongUsage("Error message.");
> }
> ```
>
> ... and this error:
>
> ```
> mixin_exception.d(19): Error: constructor 
> `mixin_exception.WrongUsage.this(string[] messages, string file 
> = __FILE__, ulong line = cast(ulong)__LINE__)` is not callable 
> using argument types `(string)`
> mixin_exception.d(19):        cannot pass argument `"Error 
> message."` of type `string` to parameter `string[] messages`
> Failed: ["/usr/bin/dmd", "-v", "-o-", "mixin_exception.d", 
> "-I."]
>
> ```
>
> Why? Why can't I have two constructors when I use mixin?
>
> If I replace mixin to real code, I have no problem:
>
> ```
> class WrongUsage : Exception {
>     this(string msg, string file = __FILE__, size_t line = 
> __LINE__) {
>         super(msg, file, line);
>     }
>
>     this(string[] messages, string file = __FILE__, size_t line 
> = __LINE__) {
>         auto msg = std.array.join(messages, "\n");
>         super(msg, file, line);
>     }
> }
> ```

mixin template create scope, for example if it was normal 
function (no ctor), you can do this:
```d

mixin template RealizeException() {
     static void foo(string){}
}

class WrongUsage{
     mixin RealizeException x;

     alias foo = x.foo;

     static void foo(string[]){}

}

void main() {
     WrongUsage.foo("Error message.");
}
```

But for ctor this doesn't work...