toString ugliness

[Jarrett Billingsley]

On Sat, Dec 6, 2008 at 12:11 PM, Jerry <jlquinn at optonline.net> wrote:
> Jarrett Billingsley Wrote:
>
>> On Sat, Dec 6, 2008 at 11:21 AM, Jerry <jlquinn at optonline.net> wrote:
>> > toString() doesn't work inside a class member function.
>> >
>> > import std.string;
>> > class A {
>> >  void f() {
>> >    string s = toString(5);
>> >  }
>> > }
>> >
>> > This errors with junk.d(19): function object.Object.toString () does not match parameter types (int)
>> >
>> > This is a nuisance and a wart (though not a bug per-se).
>> >
>> > If the language really can't handle distinguishing this.toString() from toString(int), then std.string.toString really should have a different name.
>
> As I'm thinking about this, why does this actually fail?  The parameter doesn't match the prototype for this.toString(), so why not match against the global function?
>
> Is this due to the behavior that override solves?  Would marking Object.toString() as override fix the problem?
>
>

As far as I know, it's because D does not use ADL (argument-dependent
lookup).  That is, it simply looks for the toString that is in the
nearest enclosing scope, and if it doesn't match - too bad.  Compare
this behavior to C++, where it would then continue on, looking for a
definition of toString that does match.  Most of the time ADL leads to
confusing behavior, which is why it was dropped in D.