[committed] C++ PATCH to add test for c++/83856

[Marek Polacek]

Tested x86_64-linux, applying to trunk.

2018-12-01  Marek Polacek  <pola...@redhat.com>

        PR c++/83856
        * g++.dg/cpp1y/lambda-generic-83856.C: New test.

diff --git gcc/testsuite/g++.dg/cpp1y/lambda-generic-83856.C 
gcc/testsuite/g++.dg/cpp1y/lambda-generic-83856.C
new file mode 100644
index 00000000000..ab82b6241aa
--- /dev/null
+++ gcc/testsuite/g++.dg/cpp1y/lambda-generic-83856.C
@@ -0,0 +1,30 @@
+// PR c++/83856
+// { dg-do compile { target c++14 } }
+
+namespace std {
+template <typename _Tp> _Tp declval();
+template <class _E> class initializer_list {
+  _E *_M_len;
+
+public:
+  unsigned long size;
+  _E begin();
+};
+template <typename, unsigned> struct array { void operator[](long); };
+} // namespace std
+
+template <class> struct simd {
+  static int size();
+  template <class F> simd(F, decltype(std::declval<F>()(0)) * = nullptr) {}
+};
+template <class V, class... F>
+void test_tuples(std::initializer_list<std::array<float, 1>> data,
+                 F... fun_pack) {
+  auto it = data.begin();
+  const int remaining = V::size();
+  [](...) {}((fun_pack([&](auto) { it[remaining]; }), 0)...);
+}
+
+void f() {
+  test_tuples<simd<float>>({}, [](simd<float>) {});
+}