This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 116a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
2024-12-19
The description of how the partial ordering of template functions is determined in 13.7.7.3 [temp.func.order] paragraphs 3-5 does not make any provision for nondeduced template parameters. For example, the function call in the following code is ambiguous, even though one template is "obviously" more specialized than the other:
template <class T> T f(int);
template <class T, class U> T f(U);
void g() {
f<int>(1);
}
The reason is that neither function parameter list allows template
parameter T to be deduced; both deductions fail, so neither
template is considered more specialized than the other and the
function call is ambiguous.
One possibility of addressing this situation would be to incorporate explicit template arguments from the call in the argument deduction using the transformed function parameter lists. In this case, that would result in finding the first template to be more specialized than the second.
Rationale (04/00):
This issue is covered in a more general context in issue 214.