Add AbstractClass type (sindresorhus#559)

orimiles5 · Mar 11, 2023 · dfb46ad · dfb46ad
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diff --git a/readme.md b/readme.md
@@ -120,6 +120,8 @@ Click the type names for complete docs.
 - [`Primitive`](source/primitive.d.ts) - Matches any [primitive value](https://developer.mozilla.org/en-US/docs/Glossary/Primitive).
 - [`Class`](source/basic.d.ts) - Matches a [`class`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes).
 - [`Constructor`](source/basic.d.ts) - Matches a [`class` constructor](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes).
+- [`AbstractClass`](source/basic.d.ts) - Matches an [`abstract class`](https://www.typescriptlang.org/docs/handbook/classes.html#abstract-classes).
+- [`AbstractConstructor`](source/basic.d.ts) - Matches an [`abstract class`](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-4-2.html#abstract-construct-signatures) constructor.
 - [`TypedArray`](source/typed-array.d.ts) - Matches any [typed array](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray), like `Uint8Array` or `Float64Array`.
 - [`ObservableLike`](source/observable-like.d.ts) - Matches a value that is like an [Observable](https://github.com/tc39/proposal-observable).
 

diff --git a/source/basic.d.ts b/source/basic.d.ts
@@ -12,6 +12,20 @@ Matches a [`class` constructor](https://developer.mozilla.org/en-US/docs/Web/Jav
 */
 export type Constructor<T, Arguments extends unknown[] = any[]> = new(...arguments_: Arguments) => T;
 
+/**
+Matches an [`abstract class`](https://www.typescriptlang.org/docs/handbook/classes.html#abstract-classes).
+
+@category Class
+*/
+export type AbstractClass<T, Arguments extends unknown[] = any[]> = AbstractConstructor<T, Arguments> & {prototype: T};
+
+/**
+Matches an [`abstract class`](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-4-2.html#abstract-construct-signatures) constructor.
+
+@category Class
+*/
+export type AbstractConstructor<T, Arguments extends unknown[] = any[]> = abstract new(...arguments_: Arguments) => T;
+
 /**
 Matches a JSON object.
 

diff --git a/test-d/abstract-class.ts b/test-d/abstract-class.ts
@@ -0,0 +1,40 @@
+import {expectAssignable, expectError} from 'tsd';
+import type {AbstractConstructor, AbstractClass} from '../index';
+
+abstract class Foo {
+	abstract fooMethod(): void;
+}
+
+abstract class Bar {
+	abstract barMethod(): void;
+}
+
+function functionRecevingAbsClass<T>(cls: AbstractClass<T>) {
+	return cls;
+}
+
+function withBar<T extends AbstractConstructor<object>>(Ctor: T) {
+	abstract class ExtendedBar extends Ctor {
+		// eslint-disable-next-line @typescript-eslint/no-empty-function
+		extendedBarMethod() {}
+	}
+	return ExtendedBar;
+}
+
+function assertWithBar() {
+	// This lacks `barMethod`.
+	// @ts-expect-error
+	class WrongConcreteExtendedBar extends withBar(Bar) {}
+
+	// This should be alright since `barMethod` is implemented.
+	class CorrectConcreteExtendedBar extends withBar(Bar) {
+		// eslint-disable-next-line @typescript-eslint/no-empty-function
+		barMethod() {}
+	}
+	expectAssignable(functionRecevingAbsClass<Bar>(withBar(Bar)));
+	expectAssignable(functionRecevingAbsClass<Bar>(CorrectConcreteExtendedBar));
+}
+
+expectAssignable(functionRecevingAbsClass(Foo));
+expectError(functionRecevingAbsClass<Bar>(Foo));
+assertWithBar();