Add 2 ACC specific attributes to Lazy

Add 2 ACC specific attributes to Lazy: [[ACC::coro_only_destroy_when_complete]]
and [[ACC::elideable_after_await]]. This is transparent to all other
non-ACC users.

async_simple/Common.h

@@ -44,6 +44,20 @@
 #endif  // __SANITIZE_ADDRESS__
 #endif  // __GNUC__
 
+#if defined(__alibaba_clang__) && \
+    __has_cpp_attribute(ACC::coro_only_destroy_when_complete)
+#define CORO_ONLY_DESTROY_WHEN_DONE [[ACC::coro_only_destroy_when_complete]]
+#else
+#define CORO_ONLY_DESTROY_WHEN_DONE
+#endif
+
+#if defined(__alibaba_clang__) && \
+    __has_cpp_attribute(ACC::elideable_after_await)
+#define ELIDEABLE_AFTER_AWAIT [[ACC::elideable_after_await]]
+#else
+#define ELIDEABLE_AFTER_AWAIT
+#endif
+
 namespace async_simple {
 // Different from assert, logicAssert is meaningful in
 // release mode. logicAssert should be used in case that

async_simple/coro/Lazy.h

@@ -474,7 +474,8 @@ class LazyBase {
 // should implement `coAwait(Executor*)` member method. Then the caller would
 // pass its executor instance to the awaitable.
 template <typename T = void>
-class [[nodiscard]] Lazy : public detail::LazyBase<T, /*reschedule=*/false> {
+class [[nodiscard]] CORO_ONLY_DESTROY_WHEN_DONE ELIDEABLE_AFTER_AWAIT Lazy
+    : public detail::LazyBase<T, /*reschedule=*/false> {
     using Base = detail::LazyBase<T, false>;
 
 public: