Type safety for functions that throw errors

[bezreyhan]

Search Terms

Suggestion

Error types
Error handling

Use Cases

Knowing if a called function could throw an error. As of now, it is not obvious if a function throws an error or not.

Examples

const errorThrower = (shouldThrow: boolean): boolean =>  {
    if (shouldThrow) {
        throw new Error('Hello');
    }

    return true
}

const caller = (): boolean => {
    return errorThrower(true);
}

There should be a type error in the function caller. The type error should warn that errorThrower could throw an error and therefor the error case should be handled.

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

[nattthebear]

duplicate #31329 #13219