Kuidas erineb rethrows kasutamine Kotlinis tavalistest throw-dest ning millised on selle eelised?

In Kotlin, the keyword rethrows is used in the signatures of higher-order functions that accept a lambda capable of throwing exceptions. It means that the function itself does not throw exceptions directly but can only "rethrow" exceptions that occur inside the passed lambda.

Differences from the usual throw:

• throw is used to throw an exception immediately.
• rethrows applies to functions that accept a code block (lambda) and guarantees that the function does not generate new exceptions, only propagates those that occurred inside the lambda.

Advantages of rethrows:

• Allows the compiler and calling code to know that exceptions can only originate from the passed lambda.
• Improves type safety and exception handling, as the function cannot throw exceptions on its own.
• Simplifies error handling when working with higher-order functions.

Example:

fun <T> runOperation(operation: () throws Exception): T rethrows {
    return operation()
}

// Here, runOperation does not throw exceptions by itself, only propagates exceptions from operation

Thus, rethrows helps explicitly indicate that the function does not generate exceptions but only passes them from the passed block.