Exhaustive Dictionary Analyzer

When defining a dictionary mapping between an enum and another type, place an [Exhaustive] attribute on the dictionary to ensure that it defines all of the values of the enum. So when in the future you add a new value, it will become a compile time error if you forgot to add it to the mapping.

Rules:

EXHAUSTIVEDICT0001

Ensures all enum values are defined in dictionaries with an enum type as the key, when attributed with the [Exhaustive] attribute

enum Color { Red, Green, Blue };

[Exhaustive]
Dictionary<Color, string> ColorToHex = new() {
    { Color.Red, "#FF0000" }
};

Here the rule will complain because we have forgotten to add a value for Color.Green and Color.Blue to the dictionary

EXHAUSTIVEDICT0002

Ensure only one value per enum key is defined in the dictionary

enum Color { Red, Green, Blue };

[Exhaustive]
Dictionary<Color, string> ColorToHex = new() {
    { Color.Red, "#FF0000" },
    { Color.Green, "#008000" },
    { Color.Blue, "#0000FF" },
    { Color.Red, "#FF0000" },
};

Here the rule will complain because we have added Color.Red twice

EXHAUSTIVEDICT0003

Attribute was placed on invalid object, it can only be used on a Dictionary where the key is an Enum.