Type guard function does not work for string literal types #7441

type Click = 'click';

function isClick(event: string): event is Click {
    return event === 'click';
}

function validateClickEvent(event: string): Click {
    if (isClick(event)) {
        return event; // this line raises a compilation error: Type 'string' is not assignable to type '"click"'
    }
    throw new Error('not click');
}

type Creature = {};
type Animal = {} & Creature;

function isAnimal(creature: Creature): creature is Animal {
    return true;
}

function validateAnimalCreature(creature: Creature): Animal {
    if (isAnimal(creature)) {
        return creature; // this line does not raise any compilation error
    }
    throw new Error('not animal');
}