Type function returns at module boundaries

Type function returns at module boundaries | BeforeMerge Rules | BeforeMerge

Why this matters

An explicit return type on exported functions pins the contract: a mistake inside the function is reported there, not as a confusing error in a distant consumer.

// Bad — inferred return can drift
export function getUser(id: UserId) {
  return db.find(id); // accidental shape change leaks to callers
}
 
// Good — contract is fixed at the boundary
export function getUser(id: UserId): Promise<User | null> {
  return db.find(id);
}

Why This Matters

Related Rules

Catch this automatically on every PR

Why this matters