A switch on a type code that appears in multiple files; the agent adding a new case must grep for every site and update each consistently or risk silent inconsistency.

Goal

Each case is a class implementing a shared interface; the agent adds a new case by adding one class, and the type system tells it what's still missing.

Before the refactoring

switch (event.kind) {
  case 'click': return onClick(event);
  case 'key':   return onKey(event);
}

After the refactoring

event.handle(); // ClickEvent and KeyEvent each implement handle()

Example source: Illustrative example written for this site, not a quotation from any source.

Pressure

Dispatch logic duplicates across files; the agent must enumerate and update every switch on every addition, with no compile-time check that the set is complete.

Tradeoff

Polymorphic dispatch is implicit at call sites — the agent can no longer see the full set of branches in one place and must enumerate subclasses across files to reason about behavior.

Relief

Adding a new variant is mechanical and the type checker enforces completeness; the agent's plan-and-execute loop for new cases is bounded.

Trap

Replacing every switch with polymorphism — including ones with two stable cases — creates a class hierarchy the agent must navigate without buying any extension flexibility.