overloading functions against function templates

[Sergey Gromov]

Thu, 30 Jul 2009 14:09:21 -0700, Walter Bright wrote:

> Currently, that can't be done. But it would be good to get it in for D2. 
> The question is, what rule to use?
> 
> I suggest that:
> 
> 1. if any functions match, then overload functions the usual way
> 
> 2. if no functions match, then overload the function templates the usual way
> 
> Or reverse the priority of the two.
> 
> What do you think?

I think regular functions should go first.

Let's take 4 functions for example:

void foo(int);
void foo(long);
void foo(T)(T);
void foo(T : int)(T);

and call foo(5);

If regular functions go first, we can order ours by match quality:

void foo(int);	<= best
void foo(long);
void foo(T : int)(T);
void foo(T)(T);	<= worst

That's OK, the worst match is the least specialized template.  But if we
consider templates first:

void foo(T : int)(T);	<= best
void foo(T)(T);
void foo(int);
void foo(long);	<= worst

What I strongly dislike about this is that a generic, non-specialized
foo(T)(T) effectively hides any non-templated and obviously more
specialized regular functions.  I think this simply won't work.