✅ Check the runtime member in every boolean/nullish handler

src/tagged-union.test.ts

@@ -216,8 +216,22 @@ test("getTaggedUnionMatcherW: boolean and nullish tags widen to the union", () =
             assert.equal(s.kind, true);
             return "yes" as const;
         },
-        false: () => 0 as const,
-        null: () => null,
+        false: (s) => {
+            expectTypeOf(s).toEqualTypeOf<{
+                readonly kind: false;
+                readonly b: number;
+            }>();
+            assert.equal(s.kind, false);
+            return 0 as const;
+        },
+        null: (s) => {
+            expectTypeOf(s).toEqualTypeOf<{
+                readonly kind: null;
+                readonly c: number;
+            }>();
+            assert.equal(s.kind, null);
+            return null;
+        },
     });
 
     // Assert