Implement new Concept Exercise: exceptions

Read docs/concept-exercises.md, docs/rationale-for-v3.md, docs/features-of-v3.md, and languages/fsharp/reference/implementing-a-concept-exercise.md before starting. Use the existing F# concept exercises and the stated prerequisites as entry points. Done means the exceptions exercise teaches the listed objectives, follows the v3 structure, and needs no representer or analyzer changes.

This issue describes how to implement the exceptions concept exercise for the F# track.

Getting started

Please please please read the docs before starting. Posting PRs without reading these docs will be a lot more frustrating for you during the review cycle, and exhaust Exercism's maintainers' time. So, before diving into the implementation, please read up on the following documents:

• The features of v3.
• Rationale for v3.
• What are concept exercise and how they are structured?

Please also watch the following video:

• The Anatomy of a Concept Exercise.

Goal

The goal of this exercise is to teach the student the basics of the Concept of Exceptions in F#.

Learning objectives

• Know what exceptions are.
• Know when an exception should be raised.
• Know how to raise (and reraise) an exception.
• Know how to catch an exception.
• Know how to use a finally block to always execute logic even when there are exceptions.
• Know the most important built-in exceptions (ArgumentException, InvalidOperationException) and built-in functions to raise them.
• Know how to define a custom exception.
• Know how to use pattern matching on types.

Out of scope

• Memory and performance characteristics.
• Know when to use exceptions vs results.

Concepts

The Concepts this exercise unlocks are:

• exceptions: know what exceptions are; know when an exception should be raised; know how to raise (and reraise) an exception; know how to catch an exception; know how to use a finally block to always execute logic even when there are exceptions; know the most important built-in exceptions (ArgumentException, InvalidOperationException) and built-in functions to raise them; know how to define a custom exception; know how to use pattern matching with exceptions; know when to use exceptions vs results.
• pattern-matching-types: know how to pattern match on a specific type.

Prerequisites

This exercise's prerequisites Concepts are:

• pattern-matching: know how to do pattern matching.
• string-formatting: know how to do string formatting (used in the failwithf function).
• inheritance: know how to inherit from a class.

Resources to refer to

Hints

• Exception handling: exception handling in F#.
• Exception introduction: introduction to exceptions in F#.

After

• Exception handling: exception handling in F#.
• Exception introduction: introduction to exceptions in F#.
• Exceptions vs Result: shows the difference between using exceptions vs Results.

Representer

This exercise does not require any specific representation logic to be added to the representer.

Analyzer

This exercise does not require any specific logic to be added to the analyzer.

Implementing

To implement this exercise, please follow these instructions.

Help

If you have any questions while implementing the exercise, please post the questions as comments in this issue.