Replace Error Code with Exception

Removes smells

Symptom

The agent finds functions returning numeric or string codes for failure; verifying error handling requires the agent to trace every caller and check whether the code is inspected.

Goal

Failures throw exceptions the agent reasons about as separate control flow; the type system marks the failure path.

Before the refactoring

function withdraw(amount) {
  if (amount > balance) return -1;
  balance -= amount;
  return 0;
}

After the refactoring

function withdraw(amount) {
  if (amount > balance) throw new InsufficientFunds();
  balance -= amount;
}

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

Pressure

Every caller is a chance to silently swallow the error; the agent verifying correctness must audit every call site for the check.

Tradeoff

Exceptions for predictable conditions misuse the mechanism; the agent ships try/catch around expected outcomes that should be values.

Relief

The agent reasons about success and failure paths separately; cleanup happens via finally / try-with; forgetting to handle no longer silently swallows.

Trap

Throwing for predictable conditions (not-found, validation failure) makes expected outcomes look like bugs to the agent reading the catch blocks.