The Sweet With

[Sergey Gromov]

Thu, 05 Mar 2009 07:38:23 -0500, Tomasz Sowiński wrote:

> Walter Bright Wrote:
> 
>> It looks nice, but has a subtle and disastrous problem. In D, arguments 
>> are fully resolved *before* overloading is done. If some of the 
>> overloads have with declarations, then there's a nightmarish problem of 
>> trying to mix overloading and argument resolution together.
> 
> Not sure if I understand right. Can you write up a simple example of the nightmare?
> 
> Tomek

I think Walter means that types of argument expressions are determined
first, and only then a set of compatible overloads is composed.  Say you
have

enum Foo { one, two }
int one;

void bar(int x);  // (1)
void bar(with Foo x);  // (2)

bar(one);

Currently, D will determine that expression 'one' is of type int, then
search for bar(int) or compatible, and will find (1).  With your
proposal, you must first find all 'bar's, determine that *some* of them
have 'with' arguments, and now what?  Infer type for the first argument
differently for (1) and (2), so that for (1) it's int, and for (2) it's
Foo?  Or add the Foo to the scope, so that the first argument is of type
Foo even for (1)?  I can't see a good solution.