[coroutines] Add noop_coroutine to <experimental/coroutine>

A recent addition to Coroutines TS (https://wg21.link/p0913) adds a pre-defined
coroutine noop_coroutine that does nothing.

This patch implements require library types in <experimental/coroutine>

Related clang and llvm patches:

https://reviews.llvm.org/D45114
https://reviews.llvm.org/D45120

llvm-svn: 329237

1 files changed, 66 insertions, 0 deletions

diff --git a/libcxx/test/std/experimental/language.support/support.coroutines/coroutine.handle/coroutine.handle.noop/noop_coroutine.pass.cpp b/libcxx/test/std/experimental/language.support/support.coroutines/coroutine.handle/coroutine.handle.noop/noop_coroutine.pass.cpp
new file mode 100644
index 00000000000..4ff9414dfdf
--- /dev/null
+++ b/libcxx/test/std/experimental/language.support/support.coroutines/coroutine.handle/coroutine.handle.noop/noop_coroutine.pass.cpp
@@ -0,0 +1,66 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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
+// XFAIL: clang-5, clang-6
+// <experimental/coroutine>
+// struct noop_coroutine_promise;
+// using noop_coroutine_handle = coroutine_handle<noop_coroutine_promise>;
+// noop_coroutine_handle noop_coroutine() noexcept;
+
+#include <experimental/coroutine>
+#include <cassert>
+#include <type_traits>
+
+namespace coro = std::experimental::coroutines_v1;
+
+static_assert(std::is_same<coro::coroutine_handle<coro::noop_coroutine_promise>, coro::noop_coroutine_handle>::value, "");
+static_assert(std::is_same<decltype(coro::noop_coroutine()), coro::noop_coroutine_handle>::value, "");
+
+// template <> struct coroutine_handle<noop_coroutine_promise> : coroutine_handle<>
+// {
+// // 18.11.2.7 noop observers
+// constexpr explicit operator bool() const noexcept;
+// constexpr bool done() const noexcept;
+
+// // 18.11.2.8 noop resumption
+// constexpr void operator()() const noexcept;
+// constexpr void resume() const noexcept;
+// constexpr void destroy() const noexcept;
+
+// // 18.11.2.9 noop promise access
+// noop_coroutine_promise& promise() const noexcept;
+
+// // 18.11.2.10 noop address
+// constexpr void* address() const noexcept;
+
+int main()
+{
+  auto h = coro::noop_coroutine();
+  coro::coroutine_handle<> base = h;
+
+  assert(h);
+  assert(base);
+
+  assert(!h.done());
+  assert(!base.done());
+
+  h.resume();
+  h.destroy();
+  h();
+  static_assert(h.done() == false, "");
+  static_assert(h, "");
+
+  h.promise();
+  assert(h.address() == base.address());
+  assert(h.address() != nullptr);
+  assert(coro::coroutine_handle<>::from_address(h.address()) == base);
+}
+