[gcc r13-5692] c++: Add fixed test [PR101071]

[gcc r13-5692] c++: Add fixed test [PR101071]

[Marek Polacek]

https://gcc.gnu.org/g:60fca1802a25034f49fa1e3769b3a5656f392e89

commit r13-5692-g60fca1802a25034f49fa1e3769b3a5656f392e89
Author: Marek Polacek <polacek@redhat.com>
Date:   Fri Feb 3 13:45:10 2023 -0500

    c++: Add fixed test [PR101071]
    
    As a happy accident, this was fixed by the recent r13-2978.
    
            PR c++/101071
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp0x/variadic-alias8.C: New test.

Diff:
---
 gcc/testsuite/g++.dg/cpp0x/variadic-alias8.C | 95 ++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)

diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic-alias8.C b/gcc/testsuite/g++.dg/cpp0x/variadic-alias8.C
new file mode 100644
index 00000000000..1d317ef8438
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic-alias8.C
@@ -0,0 +1,95 @@
+// PR c++/101071
+// { dg-do compile { target c++11 } }
+// { dg-additional-options "-fno-elide-constructors -O2" }
+
+// Like variadic-alias2.C, just different options.
+
+template<class...>
+struct list {};
+
+struct nil;
+
+////////////////////////////////////////////////////////////////////////////////
+
+template<int n>
+struct number {
+  constexpr /*implicit*/ operator int() const { return n; }
+  using type = number<n>;
+};
+
+using false_ = number<0>;
+using true_ = number<1>;
+
+static_assert(!false_{}, "");
+static_assert(true_{}, "");
+
+template<int... ns> using numbers = list<number<ns>...>;
+
+////////////////////////////////////////////////////////////////////////////////
+
+template<class lhs, class rhs>
+struct less_impl;
+
+template<int lhs, int rhs>
+struct less_impl<number<lhs>, number<rhs>>
+  : number<(lhs < rhs)> {};
+
+template<class lhs, class rhs> using less = typename less_impl<lhs, rhs>::type;
+
+////////////////////////////////////////////////////////////////////////////////
+
+template<class v0, class... vs>
+struct sum_impl {
+  static_assert(sizeof...(vs) == 0, "see specialization");
+  using type = v0;
+};
+
+template<int v0, int v1, class... vs>
+struct sum_impl<number<v0>, number<v1>, vs...>
+  : sum_impl<number<v0 + v1>, vs...> {};
+
+template<class... nums> using sum = typename sum_impl<nums...>::type;
+
+////////////////////////////////////////////////////////////////////////////////
+
+template<class num>
+struct conditional_impl {
+  static_assert(num{}, "see specialization");
+
+  template<class T, class F>
+  using type = T;
+};
+
+template<>
+struct conditional_impl<false_> {
+  template<class T, class F>
+  using type = F;
+};
+
+template<class num, class T, class F>
+using conditional = typename conditional_impl<num>::template type<T, F>;
+
+////////////////////////////////////////////////////////////////////////////////
+
+template<class seq>
+struct min_filter_impl;
+
+template<class... nums>
+struct min_filter_impl<list<nums...>> {
+  template<class num>
+  using count_better_mins = sum<less<nums, num>...>;
+
+  using type = list<conditional<count_better_mins<nums>, nil, nums>...>;
+};
+
+template<class seq> using min_filter = typename min_filter_impl<seq>::type;
+
+////////////////////////////////////////////////////////////////////////////////
+
+void test_min_filter() {
+  using computed = min_filter<numbers<2, 7, 2>>;
+  using expected = list<number<2>, nil, number<2>>;
+  (void)(computed{} = expected{});// compiles for identical types
+}
+
+int main() {}