Implement P0513R0 - "Poisoning the Hash"

Summary:
Exactly what the title says.

This patch also adds a `std::hash<nullptr_t>` specialization in C++17, but it was not added by this paper and I can't find the actual paper that adds it.

See http://wg21.link/P0513R0 for more info.

If there are no comments in the next couple of days I'll commit this

Reviewers: mclow.lists, K-ballo, EricWF

Reviewed By: EricWF

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D28938

llvm-svn: 292684

2 files changed, 28 insertions, 1 deletions

diff --git a/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.id/enabled_hashes.pass.cpp b/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.id/enabled_hashes.pass.cpp
new file mode 100644
index 00000000000..9799467c452
--- /dev/null
+++ b/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.id/enabled_hashes.pass.cpp
@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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: libcpp-has-no-threads
+// UNSUPPORTED: c++98, c++03
+
+// <thread>
+
+// Test that <thread> provides all of the arithmetic, enum, and pointer
+// hash specializations.
+
+#include <thread>
+
+#include "poisoned_hash_helper.hpp"
+
+int main() {
+  test_library_hash_specializations_available();
+  {
+    test_hash_enabled_for_type<std::thread::id>();
+  }
+}
diff --git a/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.id/thread_id.pass.cpp b/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.id/thread_id.pass.cpp
index 106c69e2e4a..f7d4deb8f98 100644
--- a/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.id/thread_id.pass.cpp
+++ b/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.id/thread_id.pass.cpp
@@ -9,7 +9,7 @@
 //
 // UNSUPPORTED: libcpp-has-no-threads
 
-// <functional>
+// <thread>
 
 // template <class T>
 // struct hash