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Add a new type Tuple<3, T> = [T, T, T] #54740
Description
Suggestion
🔍 Search Terms
tupel
✅ Viability 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, new syntax sugar for JS, etc.)
- This feature would agree with the rest of TypeScript's Design Goals.
⭐ Suggestion
Add a Tuple type where we can dynamically create tuples:
type Tuple<L, T> = [T, T, T]; // L = Length of Tuple📃 Motivating Example
This type would be in the same area as the Awaited type because it helps preventing complex type definitions.
Tupel-types currently have to be created manually each time. Especially for longer fix length arrays, this gets complicated really fast:
type FixLength6Array = [number, number, number, number, number, number] ;
const fixLength6Array: FixLength6Array = [1,2,3,4,5,6];By using a Tuple type, we could fix this:
type FixLength6Array = Tuple<6, number>;Also if we wanted to change the type of this tuple, this is done easily and has to be done in one place:
type FixLength6Array = Tuple<6, number | string>;💻 Use Cases
What do I want to use this for?
One example would be an rgb-type which allows numbers and strings. It currently looks like this:
type NumberString = string | number;
type RgbTuple = [NumberString, NumberString, NumberString];We could make this much simpler like this:
type RgbTuple = Tuple<3, NumberString>;
Activity
olivermrose commentedon Jun 22, 2023
#51841 (comment)
nmain commentedon Jun 22, 2023
But is the request here just a simple utility type? As far as I know, there's no way you can write
Tuple<L, T>in your own code right now.T[] & { length: L }doesn't stop you from indexing outside of the expected range.fatcerberus commentedon Jun 22, 2023
If the request is more than just the utility type then this is an essentially a duplicate of #47874 with different syntax.
fatcerberus commentedon Jun 22, 2023
As for the utility type itself, apparently you can already implement it today: #47874 (comment)
RyanCavanaugh commentedon Jun 22, 2023
I really recommend the lookup type method over tail-recursion wizardry in any case where you have a reasonable finite bound; it's generally more performant and easier to read.