test for pair piecewise construction

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@133667 91177308-0d34-0410-b5e6-96231b3b80d8

test/utilities/utility/pairs/pair.piecewise/piecewise_construct.pass.cpp

@@ -15,8 +15,41 @@
 // constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();
 
 #include <utility>
+#include <tuple>
+#include <cassert>
+
+class A
+{
+    int i_;
+    char c_;
+public:
+    A(int i, char c) : i_(i), c_(c) {}
+    int get_i() const {return i_;}
+    char get_c() const {return c_;}
+};
+
+class B
+{
+    double d_;
+    unsigned u1_;
+    unsigned u2_;
+public:
+    B(double d, unsigned u1, unsigned u2) : d_(d), u1_(u1), u2_(u2) {}
+    double get_d() const {return d_;}
+    unsigned get_u1() const {return u1_;}
+    unsigned get_u2() const {return u2_;}
+};
 
 int main()
 {
-    std::piecewise_construct_t p = std::piecewise_construct;
+#ifndef _LIBCPP_HAS_NO_VARIADICS
+    std::pair<A, B> p(std::piecewise_construct,
+                      std::make_tuple(4, 'a'),
+                      std::make_tuple(3.5, 6u, 2u));
+    assert(p.first.get_i() == 4);
+    assert(p.first.get_c() == 'a');
+    assert(p.second.get_d() == 3.5);
+    assert(p.second.get_u1() == 6u);
+    assert(p.second.get_u2() == 2u);
+#endif
 }