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Throw Statement

The throw statement explicitly raises runtime errors.

Why this exists​

Throw allows functions to signal failure conditions to callers, enabling proper error handling and recovery.

How it works​

Throw takes an expression that becomes the error value. Execution stops and the error propagates up the call stack.

Examples​

fn validateAge(age) {
  check age < 0 {
    throw "Age cannot be negative"
  }
  check age > 150 {
    throw "Age seems unrealistic"
  }
  return age
}

fn createUser(name, age) {
  check typeof(name) != "string" {
    throw "Name must be a string"
  }
  set validAge = validateAge(age)
  return { name: name, age: validAge }
}

try {
  set user = createUser("Alice", -5)
} catch error {
  say "User creation failed: " + error
}

Common mistakes​

  • Throwing non-string values
  • Not providing descriptive error messages
  • Using throw for control flow instead of errors