Programming languages enthusiast. Author of Learn Type Driven Development: https://www.packtpub.com/application-development/learn-type-driven-development
Oh I see what you mean now–and why the interface type works! Because an object with type:
interfaceCommon{a:number,b:string,}
... can always be safely downcast to its subtype type HasExtra = Common & {c?: string}. In fact now I'm surprised the type version doesn't work, ha ha. In any case, yeah I recommend to looking at interfaces more heavily. The doc page doesn't mention this but they can be used to model the shapes of not just classes but also 'POJOs', just like in TypeScript. This gives them quite a wide variety of use cases.
Programming languages enthusiast. Author of Learn Type Driven Development: https://www.packtpub.com/application-development/learn-type-driven-development
Oh I see what you mean now–and why the interface type works! Because an object with type:
... can always be safely downcast to its subtype
type HasExtra = Common & {c?: string}. In fact now I'm surprised the type version doesn't work, ha ha. In any case, yeah I recommend to looking at interfaces more heavily. The doc page doesn't mention this but they can be used to model the shapes of not just classes but also 'POJOs', just like in TypeScript. This gives them quite a wide variety of use cases.So, it turns out that (from my understanding) interfaces allow structural subtyping which distincts themselves from types.
Although, I run into this error that I don't quite understand, but looks interesting..
Wow, yeah that's a head-scratcher. No idea what's happening there!