Imported Upstream version 5.10.0.47

Former-commit-id: d0813289fa2d35e1f8ed77530acb4fb1df441bc0

mcs/errors/cs8177.cs

@@ -0,0 +1,15 @@
+// CS8177: Async methods cannot use by-reference variables
+// Line: 12
+
+using System.Threading.Tasks;
+
+class X
+{
+	int x;
+
+	async Task Test ()
+	{
+		ref int y = ref x;
+		await Task.Yield ();
+	}
+}