Imported Upstream version 5.8.0.22

Former-commit-id: df344e34b07851d296efb3e6604c8db42b6f7aa3

mcs/tests/test-pattern-08.cs

@@ -0,0 +1,32 @@
+using System.Collections.Generic;
+
+class Expr
+{
+	public int Field;
+	public Expr Next;
+}
+
+static class X
+{
+	public static IEnumerable<int> Test (this Expr expr)
+	{
+		var exprCur = expr;
+		while (exprCur != null)
+		{
+			if (exprCur is Expr list)
+			{
+				yield return list.Field;
+				exprCur = list.Next;
+			}
+			else
+			{
+				yield return 2;
+				yield break;
+			}
+		}
+	}
+
+	public static void Main ()
+	{
+	}
+}