https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117293
Bug ID: 117293
Summary: SFINAE in class partial specialization "leaks" its
side-effects
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: m.cencora at gmail dot com
Target Milestone: ---
It seems like the deprecation warning is kept even if triggered due to failed
substitution in context of class partial specialization.
In other SFINAE contexts (e.g. a dummy template param of Bar constructor) the
deprecation warning is correctly not reported.
Following code compiles without a problem on clang.
> cat a.cpp
template <typename T>
T declval();
template<typename Src, typename Dst, typename>
struct overload_set;
template<typename Src, typename Dst>
struct overload_set<Src, Dst, decltype(void(Dst{declval<Src>()}))>
{
using type = void;
};
struct string
{};
struct Foo
{
[[deprecated("dupa")]] Foo(const string&)
{};
};
struct Bar
{
template <typename U, typename overload_set<const U&, Foo, void>::type* =
nullptr>
Bar(const U&);
Bar(const string&);
};
int main()
{
string a;
Bar b{a};
}
> g++ -std=c++17 -Wall -Wextra -Werror a.cpp
This was reduced from custom implementation of variant, but I see that
libstdc++ variant uses similar impl with _Build_FUN so may be affected as well.
