using a typedefed variable with library classes

[Sergey Gromov]

Tue, 13 Jan 2009 05:59:58 +0900, Bill Baxter wrote:

> On Tue, Jan 13, 2009 at 1:48 AM, Sergey Gromov <snake.scaly at gmail.com> wrote:
> 
>> However, with a typedef, LocalType is a distinct type.  Yes it casts to
>> int implicitly, but likewise it casts implicitly to char, short and
>> long.  So compiler gets a whole load of File.write() functions matching
>> with conversions, and fails because of the ambiguity.
>>
>> That's how the language works, and it's pretty consistent IMO.  What you
>> can do is:
> 
> But the difference is LocalType can be converted to int exactly in all
> cases.  Given a choice of int,char,short,etc.  clearly the conversion
> to int is best choice.  It may be consistent with other cases
> involving multiple legal conversions, but usually you don't have such
> a single clearly preferred conversion.   It seems to significantly
> reduce the utility of typedef.

It's about overload resolution rules.  The specs say:

  The levels of matching are:
  * no match
  * match with implicit conversions
  * exact match

There is no notion of 'best' implicit conversion.