Extended: SE-0413 Typed throws

[scanon (Steve Canon)]

The review period for SE-0413 was scheduled to end today. I am extending it for another week to allow discussion of a late-breaking modification suggested by @beccadax to allow explicit specification of what type may be thrown by a do block. The review period now runs through December 7.

The following post on the original thread links to the PR updating the proposal:

SE-0413: Typed throws

I've put up a pull request adding this syntax and its semantics to the proposal document. There are a few more details there that should help clarify what Becca's proposal means for typed throws. Personally, I think this is an important addition---it means that all contexts in which an error is thrown can be explicitly typed, which is a good end state. Doug

Thanks to everybody who has contributed to the review so far!

[Paul_Cantrell]

To save folks a few clicks, proposed syntax & discussion:

SE-0413: Typed throws

An alternative might be to specify the type not in the catch clause's pattern, but as an effect on the do block instead: do throws(CatError) { try callCats() } catch let myError { ... } You might even be able to apply the typed throws effect to a catch-less do statement if you simply want to state the allowable error type explicitly.

Proposal diff:

[0413] Add `do throws(MyError)` { ... } syntax to allow explicit specification of the thrown error type in a `do...catch`.

Thumbs up on the modification here, both the idea and the syntax.

[griotspeak (TJ Usiyan)]

+1 I think this change works well. The type of the error instance is farther away in terms of lines but the clarity of throws(ErrorType) makes that a non-issue for me.

[xwu (Xiaodi Wu)]

Hi all, this is an announcement post; the review thread continues over in the original.