Make the type of caught errors unknown instead of any

[devlato]

Search Terms

catch
unknown
any
catch statement
catch type

Suggestion

Hey, I've noticed that the type of a caught error is any. Should it be unknown instead?

Use Cases

I think the any type makes no real sense in terms of helping process the errors. The unknown has been designed in order to help devs ensure that they narrow down the types properly when the real type is unclear. I believe this type would fit perfectly to the catch statement.

Examples

try {
  somethingThatFailsAndProbablyThrowsAnError();
} catch (e) {
  // e is of unknown type instead of any type, to make devs narrow down the type
  // when they want to do something with the error
  // We have to narrow down the type, before using the value
  if (e instanceof Error) {
    // ... okay
  }
}

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.

[MartinJohns]

This wouldn't be a breaking change in existing TypeScript/JavaScript code

It would be a heavy breaking change, and that's why it wasn't changed.

[devlato]

@MartinJohns Could this be introduced behind a configuration flag then? Ie. --noCatchAny 🙂

[RyanCavanaugh]

Duplicate #26174