From 0ee1ab15c237ffb50be1a5ce9c5e542b16df4d12 Mon Sep 17 00:00:00 2001
From: Iain Sandoe <iain@sandoe.co.uk>
Date: Sat, 2 Oct 2021 12:44:01 +0100
Subject: [PATCH] coroutines: Look through NOPs for awaiter variables [PR
 99575].

There was a missing STRIP_NOPS which meant that, in some cases,
an awaiter variable could be hidden by a view-convert-expr.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>

	PR c++/99575

gcc/cp/ChangeLog:

	* coroutines.cc (build_co_await): Strip NOPs from
	candidate awaiter expressions before testing to see
	if they need a temporary.

gcc/testsuite/ChangeLog:

	* g++.dg/coroutines/pr99575.C: New test.
---
 gcc/cp/coroutines.cc                      |  1 +
 gcc/testsuite/g++.dg/coroutines/pr99575.C | 35 +++++++++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/coroutines/pr99575.C

diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
index 2f45575bd92c..876a14606f83 100644
--- a/gcc/cp/coroutines.cc
+++ b/gcc/cp/coroutines.cc
@@ -1008,6 +1008,7 @@ build_co_await (location_t loc, tree a, suspend_point_kind suspend_kind)
     }
 
   /* Only build a temporary if we need it.  */
+  STRIP_NOPS (e_proxy);
   if (TREE_CODE (e_proxy) == PARM_DECL
       || (VAR_P (e_proxy) && !is_local_temp (e_proxy)))
     {
diff --git a/gcc/testsuite/g++.dg/coroutines/pr99575.C b/gcc/testsuite/g++.dg/coroutines/pr99575.C
new file mode 100644
index 000000000000..d5f86c1812ee
--- /dev/null
+++ b/gcc/testsuite/g++.dg/coroutines/pr99575.C
@@ -0,0 +1,35 @@
+
+#include <coroutine>
+
+class Task {
+ public:
+  struct promise_type {
+    Task get_return_object() { return Task{}; }
+    std::suspend_always initial_suspend() { return {}; }
+    std::suspend_always final_suspend() noexcept { return {}; }
+    void unhandled_exception() {}
+    void return_void() {}
+  };
+
+  bool await_ready() const { return false; }
+  void await_suspend(std::coroutine_handle<void> continuation) {}
+  void await_resume() {}
+};
+
+class NonMoveableTask {
+ public:
+  NonMoveableTask() = default;
+  NonMoveableTask(const NonMoveableTask&) = delete;
+  NonMoveableTask(NonMoveableTask&&) = delete;
+
+  NonMoveableTask& operator=(const NonMoveableTask&) = delete;
+  NonMoveableTask& operator=(NonMoveableTask&& other) = delete;
+
+  bool await_ready() const { return false; }
+  void await_suspend(std::coroutine_handle<void>) {}
+  void await_resume() {}
+};
+
+Task Foo(NonMoveableTask* task) { co_await* task; }
+
+int main() {}
-- 
2.47.2