Replying to @coderbyheart@wolframkriesing@typescriptlang Example:https://www.typescriptlang.org/play/index.html#src=type%20f%20%3D%20(x%3A%20string)%20%3D%3E%20boolean%0D%0A%0D%0Aconst%20myf%3Af%20%3D%20function%20myf%20(x%3A%20string)%20%7B%0D%0A%20%20%20%20return%200%3B%20%2F%2F%20invalid%0D%0A%7D Sun, 05 Aug 2018 20:53:34 UTC♥ 1