Like this: https://www.typescriptlang.org/play/?#code/GYVwdgxgLglg9mABAWwJ4DFwQBQA8BciUATiAKYCUhYIyARmcQNwBQoksCKGWehwAQwA2AZ0qERJGGADmrdtHhI0mSH0R04cIWQFgqiGv

Like this: https://www.typescriptlang.org/play/?#code/GYVwdgxgLglg9mABAWwJ4DFwQBQA8BciUATiAKYCUhYIyARmcQNwBQoksCKGWehwAQwA2AZ0qERJGGADmrdtHhI0mSH0R04cIWQFgqiGvUaIAPoknFpMxAG8WiR4hjBEeCnYdPvxMlBDESAAsAEys3gC+iGSiZJ7ePn4BSABEABIxQnAp4U4RLPlsWJxIIGIAasLk6prauvrxTi5uuB72CU6+-oGIKQAqABZxRgzERDDIZCJEAO5whCmIANRuKrytiABUiCEUuY5RMWKNHV3JvYNxkyIiAjJxMCILy9yqOK37iPn5QA https://www.typescriptlang.org/play/?#code/GYVwdgxgLglg9mABA... It's a bit of a hack, though - if you incorrectly implement myFunc so that, say, it returns a string even when x is true, it can violate the overloading assertions without any error or warning.