[test] Cleanup nullopt_t tests

* Update specification text from N4387

* Delete not_brace_initializable.fail.cpp: it's redundant with nullopt_t.fail.cpp

* is_empty<T> implies is_class<T>

* is_literal is deprecated; directly verify that we can create a nullopt_t in a constexpr context

Differential Revision: D37024

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@312256 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/utilities/optional/optional.nullopt/not_brace_initializable.fail.cpp

@@ -1,25 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     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.
-//
-//===----------------------------------------------------------------------===//
-
-// UNSUPPORTED: c++98, c++03, c++11, c++14
-// <optional>
-
-// struct nullopt_t{see below};
-
-#include <optional>
-
-using std::optional;
-using std::nullopt_t;
-
-int main()
-{
-    // I roughly interpret LWG2736 as "it shall not be possible to copy-list-initialize nullopt_t with an
-    // empty braced-init-list."
-    nullopt_t foo = {};
-}

test/std/utilities/optional/optional.nullopt/nullopt_t.fail.cpp

@@ -11,15 +11,13 @@
 // <optional>
 
 // struct nullopt_t{see below};
-// constexpr nullopt_t nullopt(unspecified);
+// inline constexpr nullopt_t nullopt(unspecified);
 
 // [optional.nullopt]/2:
-//   Type nullopt_t shall not have a default constructor or an initializer-list constructor.
-//   It shall not be an aggregate and shall be a literal type.
-//   Constant nullopt shall be initialized with an argument of literal type.
+//   Type nullopt_t shall not have a default constructor or an initializer-list
+//   constructor, and shall not be an aggregate.
 
 #include <optional>
-#include "test_macros.h"
 
 int main()
 {

test/std/utilities/optional/optional.nullopt/nullopt_t.pass.cpp

@@ -11,33 +11,30 @@
 // <optional>
 
 // struct nullopt_t{see below};
-// constexpr nullopt_t nullopt(unspecified);
+// inline constexpr nullopt_t nullopt(unspecified);
 
 // [optional.nullopt]/2:
-//   Type nullopt_t shall not have a default constructor or an initializer-list constructor.
-//   It shall not be an aggregate and shall be a literal type.
-//   Constant nullopt shall be initialized with an argument of literal type.
+//   Type nullopt_t shall not have a default constructor or an initializer-list
+//   constructor, and shall not be an aggregate.
 
 #include <optional>
 #include <type_traits>
 
-using std::optional;
 using std::nullopt_t;
 using std::nullopt;
 
-constexpr
-int
-test(const nullopt_t&)
+constexpr bool test()
 {
-    return 3;
+    nullopt_t foo{nullopt};
+    (void)foo;
+    return true;
 }
 
 int main()
 {
-    static_assert(( std::is_class<nullopt_t>::value), "");
-    static_assert(( std::is_empty<nullopt_t>::value), "");
-    static_assert(( std::is_literal_type<nullopt_t>::value), "");
-    static_assert((!std::is_default_constructible<nullopt_t>::value), "");
+    static_assert(std::is_empty_v<nullopt_t>);
+    static_assert(!std::is_default_constructible_v<nullopt_t>);
 
-    static_assert(test(nullopt) == 3, "");
+    static_assert(std::is_same_v<const nullopt_t, decltype(nullopt)>);
+    static_assert(test());
 }