Implement deduction guides for <array>; Reviewed as https://reviews.llvm.org/D46964

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@332768 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/containers/sequences/array/array.cons/deduct.pass.cpp

@@ -0,0 +1,58 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <array>
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+// UNSUPPORTED: libcpp-no-deduction-guides
+
+
+// template <class T, class... U>
+//   array(T, U...) -> array<T, 1 + sizeof...(U)>;
+//
+//  Requires: (is_same_v<T, U> && ...) is true. Otherwise the program is ill-formed.
+
+
+#include <array>
+#include <cassert>
+#include <cstddef>
+
+#include "test_macros.h"
+
+int main()
+{
+//  Test the explicit deduction guides
+    {
+    std::array arr{1,2,3};  // array(T, U...)
+    static_assert(std::is_same_v<decltype(arr), std::array<int, 3>>, "");
+    assert(arr[0] == 1);
+    assert(arr[1] == 2);
+    assert(arr[2] == 3);
+    }
+
+    {
+    const long l1 = 42;
+    std::array arr{1L, 4L, 9L, l1}; // array(T, U...)
+    static_assert(std::is_same_v<decltype(arr)::value_type, long>, "");
+    static_assert(arr.size() == 4, "");
+    assert(arr[0] == 1);
+    assert(arr[1] == 4);
+    assert(arr[2] == 9);
+    assert(arr[3] == l1);
+    }
+
+//  Test the implicit deduction guides
+  {
+  std::array<double, 2> source = {4.0, 5.0};
+  std::array arr(source);   // array(array)
+    static_assert(std::is_same_v<decltype(arr), decltype(source)>, "");
+    static_assert(std::is_same_v<decltype(arr), std::array<double, 2>>, "");
+    assert(arr[0] == 4.0);
+    assert(arr[1] == 5.0);
+  }
+}