镜像站点 · 本页由第三方 GitHub 只读镜像提供，非 GitHub 官方站点，不接受任何登录或凭据输入。前往 github.com
Skip to content

typeof class #41581

Open
Open
typeof class#41581
Assignees
DanielRosenwasserahejlsberg
Labels
Awaiting More FeedbackThis means we'd like to hear from more people who would be helped by this featureNeeds ProposalThis issue needs a plan that clarifies the finer details of how it could be implemented.SuggestionAn idea for TypeScript

Description

@DanielRosenwasser
Daniel Rosenwasser (DanielRosenwasser)
opened on Nov 18, 2020

Anders Hejlsberg (@ahejlsberg) has had a few experiments to try to make it easier to describe the type of a class. Specifically:

  • avoiding the awkward static/instance pattern that users need to write on anonymous object types/interface types

    var Thing: {
  new () => {
    instanceField: number;
  }
  staticField: string;
}

  • allowing users to describe types with class-specific characteristics (e.g. abstract)

The idea is to allow typeof to be followed by a class expression.

var Thing: typeof class Thing {
  static staticField: string;

  instanceField: number;
  constructor() {}
}

There are definitely some subtleties here. For example, handling loops and whether this syntax is allowed in JSDoc with a TypeScript-annotated class:

/** @type { typeof class C<T> { x: T } } */
//                        ^^^    ^^^
// TypeScript type parameters and annotations
// Are these allowed?
var Thing;

Activity

  1. Daniel Rosenwasser (DanielRosenwasser)
    added
    SuggestionAn idea for TypeScript
    Needs ProposalThis issue needs a plan that clarifies the finer details of how it could be implemented.
    Awaiting More FeedbackThis means we'd like to hear from more people who would be helped by this feature
    on Nov 18, 2020
  2. Daniel Rosenwasser (DanielRosenwasser)
    assigned
    Daniel Rosenwasser (DanielRosenwasser)
    and
    Anders Hejlsberg (ahejlsberg)
    on Nov 18, 2020

  3. ExE-Boss commented on Nov 19, 2020

    @ExE-Boss
    ExE Boss (ExE-Boss)
    on Nov 19, 2020
    Contributor

    Would this make it possible to revisit microsoft/TypeScript-DOM-lib-generator#858 and #39504 (comment)?

  4. jakebailey commented on Nov 21, 2023

    @jakebailey
    Jake Bailey (jakebailey)
    on Nov 21, 2023
    Member

    This is coming up again for isolated declarations; what is preventing us from emitting for class expressions in d.ts initializers, then referencing them that way?

    export const a = class A {
    readonly a: A = new A();
}

// emits as

export const a = class A {
    readonly a: A;
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Metadata

Metadata

Assignees

Labels

Awaiting More FeedbackThis means we'd like to hear from more people who would be helped by this featureNeeds ProposalThis issue needs a plan that clarifies the finer details of how it could be implemented.SuggestionAn idea for TypeScript

Type

No type

Projects

No projects

    Milestone

    No milestone

    Relationships

    None yet

    Development

    No branches or pull requests

    Issue actions