Add samples of the expected behavior to the 2019-9-11 notes

meetings/2019/LDM-2019-09-11.md

@@ -144,7 +144,78 @@ T M<T>()
 
 Let's implement the "state after assignment" rule as defined and implement the
 "Alternative" proposal outlined above. We will consider updating to use the
-"three state domain" above later, which may have some further changes.
+"three state domain" above later, which may have some further changes. A sample
+of the expected behavior follows:
+
+Non-Generic
+
+```C#
+
+using System;
+using System.Diagnostics.CodeAnalysis;
+
+class Widget {
+    string _description = string.Empty;
+
+    [AllowNull]
+    string Description {
+        get => _description;
+        set => _description = value ?? string.Empty;
+    }
+
+    static void Test(Widget w) {
+        w.Description = null; // ok
+        Console.WriteLine(w.Description.ToUpper()); // ok
+
+        if (w.Description == null) {
+            Console.WriteLine(w.Description.ToUpper()); // warning
+        }
+    }
+}
+```
+
+Generic
+
+```C#
+using System;
+using System.Diagnostics.CodeAnalysis;
+
+class Box<T> {
+    T _value;
+
+    [AllowNull]
+    T Value {
+        get => _value;
+        set {
+            if (value != null) {
+                _value = value;
+            }
+        }
+    }
+    
+    static void TestConstrained<U>(Box<U> box) where U : class {
+        box.Value = null; // ok
+        Console.WriteLine(box.Value.ToString()); // ok
+
+        if (box.Value == null) {
+            Console.WriteLine(box.Value.ToString()); // warning
+        }
+    }
+
+    static void TestUnconstrained<U>(Box<U> box, U value) {
+        box.Value = default(U); // 'default(U)' always produces a warning when U could be a non-nullable reference type
+        Console.WriteLine(box.Value.ToString()); // ok
+
+        box.Value = value; // ok
+        Console.WriteLine(box.Value.ToString()); // ok
+
+        if (box.Value == null) {
+            Console.WriteLine(box.Value.ToString()); // warning
+        }
+    }
+}
+```
+
 
 
 ## More triage