Add Examples / Unit Tests for Exceptions

[JakubSchwenkbeck]

Motivation

Resolves #480
This module demonstrates exception handling combinators in Effekt using a simple, focused example. By showcasing custom exception handling (TestException) with different strategies (default handling, ignoring, reporting, finalizing), it provides a practical guide for understanding these features.

Changes

• Introduced TestException as a custom exception type, independent of other exceptions like OutOfBounds.
• Added generalOperation, which raises a TestException for invalid input or returns a string.
• Included tests for handling exceptions with:
  • Default behavior
  • Ignoring exceptions
  • Reporting exceptions
  • Finalization hooks
  • "Reifying" with Results

Testing

The examples are self-contained in the main function, covering all provided exception-handling strategies. Each approach is tested and outputs expected results for validation (combinators.check).

[JakubSchwenkbeck]

Test Error: for llvm and chez-callcc the functions MissingValue() and raise("Some Text") seem to not be supported

Currently working on better and more natural examples which occur in the programflow without the need of these two functions

[jiribenes]

I'm not sure about the value of testing all the different exceptions as in types: Exception[E] is generic in E, so once you test one, you've tested them all by parametricity ;).
I'd guess the more important thing is testing all of the on[E].xyz combinators here:

effekt/libraries/common/exception.effekt

Lines 108 to 121 in 112bc87

	def ignore[E](proxy: on[E]) { prog: => Unit / Exception[E] }: Unit =
	ignore[E] {prog}
	def default[E, T](proxy: on[E]) { d: => T } { prog: => T / Exception[E] }: T =
	default[E, T] {d} {prog}
	def panic[E, T](proxy: on[E]) { prog: => T / Exception[E] }: T =
	panicOn[E, T] {prog}
	def report[E](proxy: on[E]) { prog: => Unit / Exception[E] }: Unit =
	report[E] {prog}
	def finalize[E, T](proxy: on[E]) { finalizer: => Unit } { prog: => T / Exception[E] }: T / Exception[E] =
	finalize[E, T] {finalizer} {prog}

/ their full versions & perhaps the one more in result.effekt too :)

[JakubSchwenkbeck]

Thank you for your input and help, I really appreciate it!
Feel free to tell me if the current approach is of more sense:)

[jiribenes]

I have a few style-related nitpicks, but otherwise LGTM, thanks!

[jiribenes]

Resolves #480.

[jiribenes]

Suggested change

	// Test for "reifying" an Exception usix^xng Result
	// Test for "reifying" an Exception using Result

typo :)

[JakubSchwenkbeck]

Thanks for looking over it!:)

[jiribenes]

Thanks, let's ship it!