3.9.spec.ts

describe('3.9', (): void => {
  describe('@ts-expect-error', (): void => {
    it('should expect error', (): void => {
      // @ts-expect-error number & string
      console.log(47 * 'octopus');
    });
    it('will fail if expect error and does not error', (): void => {
      // @ts -expect-error note had to insert space so continue to build
      console.log(1 + 1);
    });
  });

  describe('stricter checks on intersections and optional properties', (): void => {
    interface A {
      a: number; // notice this is 'number'
    }

    interface B {
      b: string;
    }

    interface C {
      a?: boolean; // notice this is 'boolean'
      b: string;
    }

    type X = A & B;
    type Y = C;

    it('should error with A & B incompatible with type C', (): void => {
      const x: X = { a: 10, b: 'test' };
      let y: Y = { a: false, b: 'no' };
      y.a = true;
      // @ts-expect-error X and Y are incompatible
      y = x;
    });
  });
});