[undefined] is assignable to number[]

[louwers]

Reproduction

import test from "ava";
import { isAssignableToValue, toSimpleType } from "../src";
import { Project } from "ts-morph";
import * as ts from "typescript";

function getType(source: string): [ts.Type, ts.TypeChecker] {
	const project = new Project({
		compilerOptions: {
			strict: true
		}
	});
	const typeChecker = project.getTypeChecker().compilerObject;

	project.createSourceFile("test.ts", source);
	const sourceFile = project.getSourceFile("test.ts")!;
	const typeAlias = sourceFile.getTypeAlias("Type");
	if (!typeAlias) throw new Error("type not found");
	return [typeAlias.getType().compilerType, typeChecker];
}

test("number[]", t => {
	const [type, typeChecker] = getType("type Type = number[]");

	t.truthy(isAssignableToValue(type, [1, 2, 3], typeChecker));
	t.truthy(isAssignableToValue(type, [], typeChecker));
	t.falsy(isAssignableToValue(type, [undefined], typeChecker));
});