LYR-SEM0137

a type named twice in one 'throws' set

error · spec 06-errors

A function's 'throws [ … ]' list names the same error type more than once.

Explanation

A throws clause is a set of error types; each one stands in it once. A repeated entry is usually a copy-paste slip, or a different type was meant.

Remove the duplicate, or name the type that was intended.

Wrong

enum Oops :: [Error] {
    Bad;
    fn message(): string { return "oops"; }
}

fn f(): int throws [Oops, Oops] { return 1; }

fn main(): void {
    let _ = try? f();
}

Right

enum Oops :: [Error] {
    Bad;
    fn message(): string { return "oops"; }
}

fn f(): int throws Oops { return 1; }

fn main(): void {
    let _ = try? f();
}