TypeEq false positive

[sirian]

TypeEq<[number, ...number[]], number[]> is true, but should be false

export type TypeEq<A, B> = (<T>() => T extends A ? 1 : 2) extends (<T>() => T extends B ? 1 : 2) ? true : false;

declare const foo: [number, ...number[]];
declare const bar: number[];

const test: TypeEq<typeof foo, typeof bar> = false;

const foobar: typeof foo = bar;
const barfoo: typeof bar = foo;

playground

[sirian]

Consider this playground

type And<T extends any[]> = T extends true[] ? true : false;

type IsExact<A, B> = [A, B] extends [B, A] ? true : false; 

export type TypeEq<A, B> = And<[
  IsExact<A, B>,
  IsExact<(<T>() => T extends A ? 1 : 2), (<T>() => T extends B ? 1 : 2)>
  ]>;

type MustBeTrue<T extends true> = T;
type MustBeFalse<T extends false> = T;

type Test = [
    MustBeTrue<TypeEq<1, 1>>,
    MustBeTrue<TypeEq<[...1[]], 1[]>>,
    MustBeTrue<TypeEq<[...0[]], 0[]>>,
    MustBeFalse<TypeEq<[0?, ...0[]], false[]>>,
    MustBeFalse<TypeEq<[0?, ...(0 | undefined)[]], (0 | undefined)[]>>,
    MustBeFalse<TypeEq<[1, ...0[]], 0[]>>
];

[kgtkr]

This is a very strange behavior.
It may be a bug of TypeScript

[kgtkr]

microsoft/TypeScript#31967