VS 2017 compatibility for enable_await_cancellation (#757)

oldnewthing · web-flow · commit 198a8270d16c · 2020-10-05T08:01:34.000-07:00
diff --git a/strings/base_coroutine_threadpool.h b/strings/base_coroutine_threadpool.h
@@ -174,7 +174,7 @@ WINRT_EXPORT namespace winrt
     struct enable_await_cancellation
     {
         enable_await_cancellation() noexcept = default;
-        enable_await_cancellation(enable_await_cancellation const&) = delete;
+        enable_await_cancellation(enable_await_cancellation const&) = default;
 
         ~enable_await_cancellation()
         {
@@ -223,7 +223,7 @@ namespace winrt::impl
     {
         decltype(get_awaiter(std::declval<T&&>())) awaitable;
 
-        notify_awaiter(T&& awaitable_arg, cancellable_promise* promise = nullptr) : awaitable(get_awaiter(static_cast<T&&>(awaitable_arg)))
+        notify_awaiter(T&& awaitable_arg, [[maybe_unused]] cancellable_promise* promise = nullptr) : awaitable(get_awaiter(static_cast<T&&>(awaitable_arg)))
         {
             if constexpr (std::is_convertible_v<std::remove_reference_t<decltype(awaitable)>&, enable_await_cancellation&>)
             {

Original file line number	Diff line number	Diff line change
`@@ -174,7 +174,7 @@ WINRT_EXPORT namespace winrt`
`174`	`174`	`struct enable_await_cancellation`
`175`	`175`	`{`
`176`	`176`	`enable_await_cancellation() noexcept = default;`
`177`		`- enable_await_cancellation(enable_await_cancellation const&) = delete;`
	`177`	`+ enable_await_cancellation(enable_await_cancellation const&) = default;`
`178`	`178`
`179`	`179`	`~enable_await_cancellation()`
`180`	`180`	`{`
`@@ -223,7 +223,7 @@ namespace winrt::impl`
`223`	`223`	`{`
`224`	`224`	`decltype(get_awaiter(std::declval<T&&>())) awaitable;`
`225`	`225`
`226`		`- notify_awaiter(T&& awaitable_arg, cancellable_promise* promise = nullptr) : awaitable(get_awaiter(static_cast<T&&>(awaitable_arg)))`
	`226`	`+ notify_awaiter(T&& awaitable_arg, [[maybe_unused]] cancellable_promise* promise = nullptr) : awaitable(get_awaiter(static_cast<T&&>(awaitable_arg)))`
`227`	`227`	`{`
`228`	`228`	`if constexpr (std::is_convertible_v<std::remove_reference_t<decltype(awaitable)>&, enable_await_cancellation&>)`
`229`	`229`	`{`