type2type/test/TStack.test.ts

TypeScript type-level data structures

import { TStack } from "..";
import { expectTypeOf } from "expect-type";

type q0 = TStack;
expectTypeOf<TStack.empty<q0>>().toEqualTypeOf<true>();
expectTypeOf<TStack.size<q0>>().toEqualTypeOf<0>();

// push
type q1 = TStack.push<TStack, 1>;
expectTypeOf<TStack.empty<q1>>().toEqualTypeOf<never>();
expectTypeOf<TStack.size<q1>>().toEqualTypeOf<1>();

// multiple push
type q4 = TStack.push<
  TStack.push<TStack.push<TStack.push<TStack, 1>, 2>, 3>,
  4
>;
expectTypeOf<TStack.empty<q4>>().toEqualTypeOf<never>();
expectTypeOf<TStack.size<q4>>().toEqualTypeOf<4>();

// peek
expectTypeOf<TStack.peek<q4>>().toEqualTypeOf<4>();
// pop
type q3 = TStack.pop<q4>;
expectTypeOf<TStack.size<q3>>().toEqualTypeOf<3>();
expectTypeOf<q3>().toEqualTypeOf<
  TStack.push<TStack.push<TStack.push<TStack, 1>, 2>, 3>
>();

// empty peek
expectTypeOf<TStack.peek<q0>>().toEqualTypeOf<never>();
// empty pop
expectTypeOf<TStack.pop<q0>>().toEqualTypeOf<TStack>();