Imported Upstream version 5.8.0.22

Former-commit-id: df344e34b07851d296efb3e6604c8db42b6f7aa3

mcs/errors/cs8139.cs

@@ -0,0 +1,18 @@
+// CS8139: `D.M()': cannot change return type tuple element names when overriding inherited member `C.M()'
+// Line: 14
+
+class C
+{
+	public virtual (int a, int b) M ()
+	{
+		throw null;
+	}
+}
+
+class D : C
+{
+	public override (int c, int d) M ()
+	{
+		throw null;
+	}
+}