http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51213
Bug #: 51213
Summary: [C++11][DR 1170] Access control checking has to be
done under SFINAE conditions
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
gcc 4.7 20111112 (experimental) in C++11 mode rejects the following code:
//---
class C {
typedef int type; // Line 2
};
template<class T, class = typename T::type>
auto f(int) -> char;
template<class>
auto f(...) -> char (&)[2];
static_assert(sizeof(f<C>(0)) == 2, "Ouch"); // Line 11
template<class T>
auto g(int) -> decltype(typename T::type(), char());
template<class>
auto g(...) -> char (&)[2];
static_assert(sizeof(g<C>(0)) == 2, "Ouch"); // Line 19
int main() {}
//---
"main.cpp|11|error: static assertion failed: "Ouch"|
main.cpp||In function 'decltype ((typename T::type(), char())) g(int) [with T =
C; decltype ((typename T::type(), char())) = char; typename T::type = int]':|
main.cpp|2|error: 'typedef int C::type' is private|
main.cpp|19|error: within this context|
main.cpp|19|error: static assertion failed: "Ouch"|"
After approval of DR 1170:
http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1170
access checking has become part of the template substitution process as
described in 14.8.2 p8:
"If a substitution results in an invalid type or expression, type deduction
fails. An invalid type or expression is one that would be ill-formed if written
using the substituted arguments. [ Note: Access checking is done as part of the
substitution process. —end note ] [..]"
This means as of C++11 above program should be accepted.
