[gcc r10-9236] libstdc++, coroutine: Add missing constexpr markers.

[Iain D Sandoe]

https://gcc.gnu.org/g:517fb88b8a96795cce3f88862148880b1c46b198

commit r10-9236-g517fb88b8a96795cce3f88862148880b1c46b198
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Sun Jul 12 20:16:21 2020 +0100

    libstdc++, coroutine: Add missing constexpr markers.
    
    The methods of the trivial awaitables are intended to
    be constexpr.
    
    libstdc++-v3/ChangeLog:
    
            * include/std/coroutine: Mark the methods of the
            trivial awaitables as constexpr.
    
    (cherry picked from commit f1b6e46c417224887c2f21baa6d4c538a25fe9fb)

Diff:
---
 libstdc++-v3/include/std/coroutine | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/libstdc++-v3/include/std/coroutine b/libstdc++-v3/include/std/coroutine
index b40a3bcf9cc..468d1107557 100644
--- a/libstdc++-v3/include/std/coroutine
+++ b/libstdc++-v3/include/std/coroutine
@@ -273,20 +273,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   /// [coroutine.trivial.awaitables]
   struct suspend_always
   {
-    bool await_ready() { return false; }
+    constexpr bool await_ready() const noexcept { return false; }
 
-    void await_suspend(coroutine_handle<>) {}
+    constexpr void await_suspend(coroutine_handle<>) const noexcept {}
 
-    void await_resume() {}
+    constexpr void await_resume() const noexcept {}
   };
 
   struct suspend_never
   {
-    bool await_ready() { return true; }
+    constexpr bool await_ready() const noexcept { return true; }
 
-    void await_suspend(coroutine_handle<>) {}
+    constexpr void await_suspend(coroutine_handle<>) const noexcept {}
 
-    void await_resume() {}
+    constexpr void await_resume() const noexcept {}
   };
 
   } // namespace __n4861