Flexibility of template literal types for enums

Search Terms

template literal type enum permutations

Suggestion

Typescript 4.1 brought template literal types, which make it simple to express all the possibilities of permutations of unions of string types concatenated together. It would be cool if there was some equivalent syntax for expressing enum key/value pairs with the same level of expressivity that template literal types provide.

Use Cases

However, my codebase right now uses enums for these kinds of string types, so if I want to express a bunch of permutations of possible values with an enum, I can't really leverage template literal types in this case.

Examples

this is just some syntax I'm making up, I don't know how this would work especially for dealing with keys and values separately:

enum Color {
  RED,
  BLUE
}
enum Shape {
  SQUARE,
  CIRCLE
}
enum ColoredShape {
  [`${keyof Color}_${keyof Shape}`]
}

console.log(ColoredShape.RED_SQUARE, ColoredShape.BLUE_CIRCLE)

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, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.
  • I think?

Commencez par examiner l’interaction proposée dans l’issue entre les template literal types et les paires clé/valeur d’enum. Le payload ne mentionne aucun fichier, test ou point d’entrée, et la syntaxe et la sémantique restent spéculatives. La tâche ne serait considérée comme terminée qu’une fois qu’une conception arrêtée des permutations d’enum ainsi qu’un plan clair d’implémentation et de validation seraient définis.