http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52072
Bug #: 52072
Summary: Several non-deduced context not recognized
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: daniel.krueg...@googlemail.com
gcc does not properly handle several situations where a non-deduced context
should occur. E.g. the following program is rejected:
//-------
template<class T>
struct ident { typedef T type; };
template<class T>
void f(T, typename ident<T>::type*); // Line 5
struct B {
typedef int* type;
operator type();
};
int main() {
f(0, B()); // Line 13
}
//-------
"In function 'int main()':|
13|error: no matching function for call to 'f(int, B)'|
13|note: candidate is:|
5|note: template<class T> void f(T, typename ident<T>::type*)|
5|note: template argument deduction/substitution failed:|
13|note: mismatched types 'typename ident<T>::type*' and 'B'|"
It seems that the compiler only accepts situations, where the *complete* type
is wrapped like in
template<class T>
void f(T, typename ident<T*>::type);
But this behaviour does not match with the wording. According to
[temp.deduct.type] p5 b1:
"The non-deduced contexts are:
— The nested-name-specifier of a type that was specified using a qualified-id."
(The same rule exists in C++03, [temp.deduct.type] p4 b1)
The behaviour of gcc looks extraordinary when compared with other compilers,
vc10, clang, or comeau online accept the original code.
