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From: fresl@grad.hr (Kresimir Fresl)
Newsgroups: comp.std.c++
Subject: Re: Problem with function template overload resolution
Date: Mon, 22 Sep 2003 17:05:00 +0000 (UTC)
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Joerg Walter wrote:

> I've already tried to discuss the following two programs on
> comp.lang.c++.moderated. Kresimir Fresl's test case
> 
> ----------
> #include <iostream>
> 
> template<typename A, typename T>
> struct result {};
> 
> template<typename T>
> struct arg1 {
>    typedef T value_type;
> };
> template<typename T>
> struct arg2 {
>    typedef T value_type;
> };
> 
> template<typename A>
> result<A, typename A::value_type> foo(A const& a) {
>    std::cout << "foo<A>" << std::endl;
>    return result<A, typename A::value_type>();
> }
> template<typename R, typename A>
> R foo(A const& a) {
>    std::cout << "foo<R, A>" << std::endl;
>    return R();
> }
> 
> int main() {
>    arg1<int> s1;
>    arg2<int> s2;
> 
>    foo(s2);    // OK
> 
>    foo<arg1<int>, arg2<int> >(s2);  // OK
>    foo<arg2<int>, arg2<int> >(s2);  // OK
> 
>    foo<arg1<int> >(s2);    // OK
>    foo<arg2<int> >(s2);    // Ambigous?
> }
> 
> ----------
> 
> is accepted by GCC 3.3.1, a program run results in
> 
> foo<A>
> foo<R, A>
> foo<R, A>
> foo<R, A>
> foo<R, A>
> 
> ICC 7.1 and MSVC 7.1 reject this code. 

And Comeau C/C++ 4.3.0.1, too.

Some time ago (in January) I asked Comeau's support team about
it. Here is their reply:
================================================================
[...] We suspect your case
is ill-formed but still need to go through that Standard more
thoroughly on it before saying so for certain, and we also want
to double check it is not impacted by any pending defect report.
================================================================

But they never said `so for certain', and, if `so', why.

Regards,

Kresimir Fresl


PS. I also tried 4.3.3 beta online:

    http://www.comeaucomputing.com/tryitout/

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