import std;

void main()
{
    struct Foo {
        string s = "string";
        alias s this;

        string toString() { return s.format!"Foo(%s)"; }
    }
    Foo().to!string.writeln;   // string
    Foo().format!"%s".writeln; // Foo(string)


    struct Bar {
        int s = 3;
        alias s this;

        T opCast(T)() { return 43; }
    }
    Bar().to!int.writeln;      // 3
    (cast(int) Bar()).writeln; // 43


    struct Baz {
        T opCast(T)() { return 43; }
    }
    Bar().to!int.writeln;      // 43
    (cast(int) Bar()).writeln; // 43
}

Is this the intended behavior of std.conv : to?
Shouldn't it only fallback to the alias this if none of those work?

On Thursday, 20 May 2021 at 16:19:02 UTC, João Lourenço wrote:

The documentation of std.conv.to doesn't mention anything about implicit conversions or alias this, so at the very least, this is a bug in the documentation.

On Thursday, 20 May 2021 at 18:27:02 UTC, Paul Backus wrote:

Or it is just an unintended side effect. The current behavior makes these functions useless.