toImpl deprecated, use opCast instead?

[Jens Mueller]

Manu wrote:
> On 7 June 2012 17:09, Jens Mueller <jens.k.mueller at gmx.de> wrote:
> 
> > Manu wrote:
> > > Seriously?
> > >
> > > I perceive to!T and cast(T) as fundamentally different operations. How
> > can
> > > opCast correctly perform the role of to! ?
> > > cast() is a low level type cast, to! implies a conversion of some kind.
> > If
> > > you have a pointer type, I assume cast to operate on the pointer, and to!
> > > to perform a conversion of the thing it represents.
> > >
> > > to!int("12345")  or  cast(int)"12345"
> > > to!JSONValue(obj)  or  cast(JSONValue)obj
> > > cast(string)obj  <- appears to be a primitive cast operator, communicates
> > > nothing to me about the expected format of the string produced
> > >
> > > The cast approach feel really wrong to me...
> > >
> > > I need to do conversion between some fairly complex types. to! feels
> > > appropriate, but cast() just seems weird...
> > > Have I missed something?
> >
> > I think the passage you are referring to applies only when converting
> > from a user defined type to a built-in type.
> > If you have user defined types only the right approach is to define a
> > constructor in the target type I think.
> > Something like this:
> >
> > struct A {}
> > struct B {
> >        this(A a)
> >        {
> >        }
> > }
> >
> > to!B(A); // will use B's constructor
> >
> > I don't know what to do if you have no control over B (besides opCast or
> > providing a specialized to! template).
> >
> 
> I have no control over B.
> I thought the idea of toImpl() was to avoid having to specialise to! ?
> I generally liked the idea, except the name toImpl seems odd (what's
> 'implicit' about an explicit conversion function?)

Then I would go with defining opCast in A if you also need implicit
conversions from A to B. If you only want explicit conversions then
define to! for that particular conversion.
I think to! and toImpl! handle most of the (common) conversion use cases
but not the case you want.
Does this still look odd to you?

Jens