copying: deep vs shallow copy module (clone() traps, copy constructors, serialization copy, records, defensive copies, collection copies), 17 contract tests

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_017ic4b4X2xx7RrveVQU9R1N

copying/src/broken/FinalFieldClone.java

@@ -0,0 +1,23 @@
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Deliberately does not compile. Not part of the Maven build; scripts/broken.sh runs javac on it
+ * and commits the compiler's own message to output/02-final-field-clone.txt.
+ *
+ * The point: a Cloneable class cannot deep-copy a final field inside clone(), because clone()
+ * is not a constructor and final fields cannot be reassigned after construction.
+ */
+public class FinalFieldClone implements Cloneable {
+    private final List<String> items = new ArrayList<>();
+
+    @Override public FinalFieldClone clone() {
+        try {
+            FinalFieldClone copy = (FinalFieldClone) super.clone();
+            copy.items = new ArrayList<>(items);   // error: cannot assign a value to final variable
+            return copy;
+        } catch (CloneNotSupportedException e) {
+            throw new AssertionError(e);
+        }
+    }
+}