HypeScript: Simplified TypeScript type system in TypeScript's own type system

Post by chrismorgan » Thu, Jul 28, 2022, 6:16 AM UTC

RussianCow wrote: post #15

p1necone wrote: post #12

Earlier quoted context omitted.

In the context of type definitions, strings aren't really regular bare strings. I.e. if I write type foo = { bar: "Vodka" } I'm guaranteeing that the value of 'bar' on any object of that type must be "Vodka" - the type of bar is not string, it's literally "Vodka" because string values can be types. This seems a little obscure and pointless, but you can put these string types in a union, and enforce that a value must…

To add to this, the reason it’s important for TypeScript to support string literals as values instead of using enums or something new is interop with existing JS. For example, think of an event handler where you pass the event name as the first argument; you can ensure at compile-time that an invalid event name isn’t passed.

Post by dfee » Thu, Jul 28, 2022, 6:29 AM UTC

noduerme wrote: post #29

This is insanely cool voodoo. But... I may be lacking in imagination here... I'm trying to think of how I'd actually use it. Maybe it'll come to me in the middle of the night 8) I do really wish TS had actual inbuilt reflective type checking along the lines of this: https://github.com/Hookyns/tst-reflect ...I can hazily see some kind of monstrosity that could come from linking these things together hah

Post by jraph » Thu, Jul 28, 2022, 7:03 AM UTC

efortis wrote: post #14

“I'm not about to start using it for real projects, it's really just a thought experiment about how nice JavaScript could be with an alternative syntax.” - jashkenas 2009 https://news.ycombinator.com/item?id=1014225

Post by rrishi » Thu, Jul 28, 2022, 7:05 AM UTC

throwaway17_17 wrote: post #5

This article is intriguing, I liked the playful tone, particularly in light of the subject. I’m hoping the talk gets streamed to YouTube. This also makes me interested in the formalization attempts I have heard are ongoing for TS’s type system. Anyone with good paper/videos on that development feel free to drop a link.

Post by ygra » Thu, Jul 28, 2022, 7:34 AM UTC

girvo wrote: post #28

theK wrote: post #10

Am I the only one that feels uncomfortable with all that usage of strings in TS’s type system? Why not use pure literals instead of string literals? This is a genuine question, I’m trying to find out what the pros and cons where in the decision making process.

As others have pointed out, they're not really "strings" per se, or at least can be a lot stricter than a string might seem when used right. We use that constantly for useful things. The bigger reason why it is this way is to ensure you can write type annotations for stringly-typed Javascript. While Typescript is it's own thing really at this point, it still is very focused on making it possible to type-annotate JS c…