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typeof class #41581
Description
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
ExE-Boss commentedon Nov 19, 2020
Would this make it possible to revisit microsoft/TypeScript-DOM-lib-generator#858 and #39504 (comment)?
jakebailey commentedon Nov 21, 2023
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?