Rule proposal: Unreachable swtich default case

[kkimdev]

Before You File a Proposal Please Confirm You Have Done The Following...

• I have searched for related issues and found none that match my proposal.
• I have searched the current rule list and found no rules that match my proposal.
• I have read the FAQ and my problem is not listed.

My proposal is suitable for this project

• My proposal specifically checks TypeScript syntax, or it proposes a check that requires type information to be accurate.
• My proposal is not a "formatting rule"; meaning it does not just enforce how code is formatted (whitespace, brace placement, etc).
• I believe my proposal would be useful to the broader TypeScript community (meaning it is not a niche proposal).

Description

When all the enum cases are listed in a switch statement, default: block is unreachable. To my knowledge, there is no existing rule that detects such cases.

Note: This could be a special case of a more general unreachable code detection rule.

Fail Cases

enum Animal {
    cow
}

const main = (animal: Animal) => {
    switch (animal) {
        case Animal.cow:
            return 3;
        default:
            return 4;
    }
};

Pass Cases

enum Animal {
    cow,
    horse
}

const main = (animal: Animal) => {
    switch (animal) {
        case Animal.cow:
            return 3;
        default:
            return 4;
    }
};

Additional Info

No response

[Josh-Cena]

Duplicate of #3616

[kkimdev]

Thanks!

PR work in progress: #7539