prefer-type-fest-constructor

Require TypeFest Constructor over explicit constructor signatures.

Targeted pattern scope

This rule reports explicit new (...args) => T signatures and prefers Constructor<T> for newable class contracts.

What this rule reports

• new (...args) => T constructor type signatures.

Detection boundaries

• ✅ Reports explicit non-abstract constructor signatures in type positions.
• ❌ Does not auto-fix when argument-generic relationships need manual preservation.

Why this rule exists

Constructor<T> is a canonical alias for class factory contracts.

Using one alias across modules keeps dependency-injection and class-registry types uniform.

❌ Incorrect

type ExplicitCtor = new (host: string, port: number) => Service;

✅ Correct

import type { Constructor } from "type-fest";

type ServiceCtor = Constructor<Service>;

Behavior and migration notes

• Constructor<T> expresses "newable" class values that produce T.
• Preserve specialized argument tuples with wrapper types when replacing explicit signatures.
• Prefer this alias in public APIs to avoid repeated constructor signature boilerplate.

ESLint flat config example

import typefest from "eslint-plugin-typefest";

export default [
    {
        plugins: { typefest },
        rules: {
            "typefest/prefer-type-fest-constructor": "error",
        },
    },
];

When not to use it

Disable this rule if your codebase intentionally prefers explicit constructor signatures over TypeFest aliases.

Package documentation

TypeFest package documentation:

Source file: source/basic.d.ts

/**
Matches a [`class` constructor](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes).

@category Class
*/

Rule catalog ID: R039

Further reading

• TypeFest README
• TypeScript Handbook: Classes

Adoption resources

• Rule adoption checklist
• Rollout and fix safety