Re: inheriting constructos

[Denis Koroskin]

On Mon, 30 Nov 2009 02:20:40 +0300, bearophile <bearophileh...@lycos.com>  
wrote:

Andrei Alexandrescu:
c) If a class doesn't define any constructors but does add at least a
non-static field -> undecided.

Does 'undecided' mean 'compile-time error'?"

Bye,
bearophile

I think it means they are not decided whether it should inherit  
constructors.

Back on topic, I do think inheriting constructors is a good idea, even in  
presence of additional fields (why not?)

I also think constructor inheritance could be implemented without any  
changes to the language the following way:

this(Args...)(Args args) if (__traits(compiles, super(args)))
{
    super(args);

    // initialize additional fields, if any present
    // and/or do some post-construction logic
}

Why create new rules? :)

The trivial way could be even simplified like this:

// just a basic idea
template InheritCtors()
{
    this(Args...)(Args args) if (__traits(compiles, super(args)))
    {
        super(args);
        static assert (this.tupleof == super.typleof); // check that no  
additional members present
    }
}


class Foo { /* a few different ctors */ }

class Bar : Foo
{
    mixin InheritCtors(); // Voilà!
}