Typed throws #swift-api

TypedThrows.swift

// MARK: - Swift 6: Typed throws

// Define a specific error type for integer parsing.
enum IntegerParseError: Error {
  case nonDigitCharacter(String, index: String.Index)
}

/// Parses a string into an integer, throwing a specific typed error if parsing fails.
///
/// - Parameter string: The string to parse.
/// - Throws: `IntegerParseError` only, making it a *typed throw*.
/// - Returns: The parsed integer value.
func parse(string: String) throws(IntegerParseError) -> Int {
  for index in string.indices {
    // Example logic: detect non-digit character and throw a typed error.
    throw IntegerParseError.nonDigitCharacter(string, index: index)
  }
  return 0
}




// Example usage:
do {
  try parse(string: "123a")
} catch let error as IntegerParseError {
  print("Failed with: \(error)")
}
// This feature aligns Swift more closely with strong static typing principles — similar to typed exceptions in languages like Rust’s Result<T, E> or Swift’s own Result enum, but applied to throws functions directly.