Re: Unexpected overload resolution under SFINAE conditions
On Mar 25, 4:43 pm, "Daniel Kr?gler" <daniel.krueg...@googlemail.com>
wrote:
// #2 ---------------------------------------------------------
#include "Common.h"
template <class T>
void foo(Something<T>&){ std::cout << "1" << std::endl; }
template <class T>
typename enable_if<is_same<T, Other>::value>::type
foo(T&) { std::cout << "2a" << std::endl; }
template <class T>
typename enable_if<!is_same<T, Other>::value>::type
foo(T&) { std::cout << "2b" << std::endl;}
Even this program compiled and gave one result ("1" again)
- except for Comeau (I tested all available online versions as
well as two versions used in our company - from here I cannot
say which versions) which choked on an *ambiguity*:
"error: more than one instance of overloaded function "foo"
matches the argument list, the choices that match are:
function template "void foo(Something<T> &)"
function template "enable_if<<expression>, void>::type
foo(T &)"
The argument types that you used are: (Something<int>)
foo(x);
^
My question is: Can Comeau be right here? I studied large parts
of 13.3/2-4, 13.3.1.1.1, 13.3.2, 13.3.3.1, 14.8.3, 14.8.2 including
a small promenade into 3.4(2), but could not find any evidence
for this outcome, but maybe my reading/interpretation is wrong.
?13.1/2 makes it clear that a function declaration may not be
overloaded by another function declaration that differs only in its
return type - yet this program overloads foo() with another a nearly-
identical foo() - that differs only in its return type. Therefore
Comeau is correct to report an error.
Greg
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