I wanted to do "instanceof SystemError" but Typescript was complaining that SystemError is undefined and I couldn't find it anywhere to import. Apparently the class itself is not exported by Node. This kind of error has some special fields, so it could be useful to have types for it.

You can't use instanceof SystemError if the class itself is not exported by Node.

The node-way to checking what error it is - checking error.code and/or error.errno. The typings already have common ErrnoException class with these fields.

Exporting SystemError interface might be useful for using in your code like (error as SystemError).address. But you can't use instanceof SystemError.

ErrNoException works fine for code specifically but it only supports 4 of the 9 properties on NodeJS's SystemError.

For example this use-case isn't supported:

try {
  functionCall();
} catch (e) {
  if (e.info) { // this line is invalid in Typescript using `strict: true`
    console.log({ info: e.info });
  }
}