Drop constructor() if it contains only super() with same arguments

[rentalhost]

Describe the feature

I have a extends Error class, but how TypeScript defines cause as unknown, I need just rewrite constructor() to set cause type as I expect. But when it is transformed into JavaScript, so it can be just dropped.

export class GenericError extends Error {
  public cause!: { value: number };

  public constructor(
    message: string,
    cause: { value: number }
  ) {
    super(message, cause);
  }
}

So, I can do that, with TS validation to number for cause:

throw new GenericError("message", { cause: 123 });

It is just transformed into (pretty-printed):

export class GenericError extends Error{
  cause;
  constructor(r,e) {
    super(r,e)
  }
}

Once constructor() just calls super() with the same args, so I think it can be safetly dropped.

https://play.swc.rs/?version=1.3.55&code=H4sIAAAAAAAAA22NQQqDMBBF94J3%2BN0peAJdl54jpoMEYhJmMkUQ796k6aKLLuf9%2F9%2FQkSJnWG9E8KBA7OydOTLoyBSegnadfQckXb2zsEaFbjNOvIxXmhF0X4lxLX33W4tBMqvNkYeKgZ1EzFYGhbuwTY1%2BdH9sNR3bY0A0EQ9fwdQ241Kz0rveS6BdBMYAAAA%3D&config=H4sIAAAAAAAAA41VwW7bMAy99ysCn3fochiGfkBv%2BwZBsShHnSwaIuUmKPLvoxU7TRva2CWI%2BfRIkXykPp52u%2BaN2uZl9yF%2F5WOwmSDfvsVC58T2JJaGzwNQm8PAzY8FZZogbyNBNV2uSMM2d8ATC2j%2FvN%2FPjCYiEiyM2daHFPz5PmaL%2FZCB6M4mVnFZekhMX%2FkzlvF9AjiXe%2FsBMYJNG4ixZEJi6CBrjluM0Q4EZrRZ8TLd1OZAqIWYwMLgzJBxUPHkAgdMEvMRdWCdadGBAoUMLYcRNJrEEloiSU%2FJp8IODqXrap%2B%2FsWG0sVhWYsKptkRuq3g9YiA2viSthFdwpQZXcC7ud2bwJgOXnB55bxjSSk%2F%2BAkgFoiVKtgfNbz3hRU9rbL%2FJDMmLZPms4KJvLcsEnRTVhOCVyk6VgcxB62YGV1qYKttq15nhlfJRcGDAe9GK4preA7dHLeg06OgVQPprvaaqK2BuU7iCTwOxAb9KlqwLbD7RWz6uo3TuDxg3AvTAR3QbB6QVjOtwli1xGtbxkhyINMCpRwpV4HEJyAAwmlj35YM2ZDzEo%2BkiHj7XxHzgctvDvU1dnfe7fck4RBghrsn4P0ZkE5W7jZOql8l%2BmF74rYnSyuCFn89fng1J5Wn5rUk1Pbpyl1DV5PU5%2BdV8HlpejqVqTaA%2FC7HW6fIP6MYcrOMGAAA%3D

https://github.com/microsoft/TypeScript/issues/54021

Babel plugin or link to the feature description

No response

Additional context

No response

[kdy1]

I don't expect this to have meaningful difference in real-world apps.

[rentalhost]

@kdy1 I found a lot of real-world examples based on same concept: to strong typing.

• https://grep.app/search?q=constructor%5Cs%2A%5C%28.%2B%5C%29%5Cs%2A%5C%7B%5Cs%2Asuper%5C%28.%2B%5C%29%5Cs%2A%3B%5Cs%2A%7D&regexp=true&filter[lang][0]=TypeScript

[rentalhost]

And if you come to reconsider this case, perhaps this can be applied under the same condition for parent methods:

class GenericLog {
    public log(info: any) {
        console.log(info);
    }
}

class NumberLog extends GenericLog {
    public log(info: number) {
        return super.log(info);
    }
}

const genericLog = new GenericLog();
genericLog.log(123); // Nice
genericLog.log('error'); // Nice

const numberLog = new NumberLog();
numberLog.log(123); // Nice
numberLog.log('error'); // Bad (because it was narrowed)

There are also cases where there will be no return, but the rule can only be applied if the parent method also doesn't return a value (as it's a more complex case, maybe it's better to just ignore it, unless there is a reliable solution for that).

class GenericAlert {
    public alert(info: any): any {
        alert(info);
        return true;
    }
}

class NumberAlert extends GenericAlert {
    // Can be entirely dropped after transform.
    public alert(info: number): any {
        return super.alert(info);
    }
}

class StringAlert extends GenericAlert {
    // CANNOT be dropped, because it returns void now.
    public alert(info: string): void {
        super.alert(info);
    }
}

const genericLog = new GenericAlert();
genericLog.alert(123); // Nice
genericLog.alert('error'); // Nice

const numberLog = new NumberAlert();
numberLog.alert(123); // Nice
numberLog.alert('error'); // Bad (because it was narrowed)

const stringLog = new StringAlert();
stringLog.alert('error'); // Nice
stringLog.alert(123); // Bad (because it was narrowed)

[NullVoxPopuli]

this''d be really great to have!

[NullVoxPopuli]

Related:

• https://github.com/swc-project/swc/issues/7336
• https://github.com/swc-project/swc/issues/8177
• https://github.com/evanw/esbuild/issues/3463
• https://github.com/evanw/esbuild/issues/3464
• https://github.com/terser/terser/issues/1467
• https://github.com/terser/terser/issues/1468