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Arrow function can be non intuitive for JS developers

See original GitHub issue

Currently y := x => x + 1 compiles to const y = x(() => x + 1) which may be a source of confusion for people coming from js which allows parenthesis to be omitted for single argument.

Should we consider adopting the js behavior by default (unless coffeeCompat is set to true) ?

Perhaps to reduce ambiguity we enforce that arg list can never be omitted, so instead of y := -> 1 we’d have to write y := () -> 1

Issue Analytics

  • State:closed
  • Created 9 months ago
  • Comments:6 (6 by maintainers)

github_iconTop GitHub Comments

STRd6commented, Dec 9, 2022

@lorefnon TypeScript doesn’t allow Type annotations on paren-less single parameters (another reason I choose to disallow them). There is definitely room to improve error messages in the LSP and I’d be happy for you to take a look.

The recommended Civet way to type annotate your example is:

z : (n: number) => number := &+1

Note the annotation is for the type of z to the left of the const assignment :=.

In cases where the ampersand function is used inline TS can usually infer the type correctly.

declare const x : number[]

y := &+1

@edemaine in light of these examples I think that allowing inline type annotation of ampersand functions makes the intent a bit less clear but I’d be happy to look at some counter examples.

Also, I want to say thank you both for your contributions! It really helps me work out the practical details of the language to see how people feel most comfortable using it.

edemainecommented, Dec 9, 2022

Would &: number + 1 or (&: number) + 1 be interesting typed shorthand for ($: number) => $ + 1?

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