typelevel-assert

<TypeLevel> Assert provides convenient assertions for type-level programming.

Usage

Installation

npm i -D typelevel-assert

Start to code (try it out)

import { assertType, Is } from 'typelevel-assert';

type Hi<T extends string> = `Hi ${T}!`;

assertType<Is<Hi<'TypeLevel'>, 'Hi TypeLevel!'>>();

The assertType<T>() assertion accepts a type parameter T.

<TypeLevel> Assert has the following built-in type predicates that can be used with assertType:

type	description
`And<C1 extends boolean, C extends boolean2>`	`true` if both `C1` and `C2` are true, `false` otherwise
`Or<C1 extends boolean, C2 extends boolean>`	`true` if any of `C1` or `C2` is true, `false` otherwise
`Not<C extends boolean>`	`true` if `C` is `false`, `true` otherwise
`Equals<T1, T2>`	`And<Extends<T1, T2>, Extends<T2, T1>>`
`Extends<T1, T2>`	syntactic sugar for `[T1] extends [T2] ? true : false`
`Is<T1, T2>`	`true` if `T1` is exactly `T2`, false otherwise