Strongly typed functional languages (including Reason) can often figure out a function's parameter types based on how the variables are used in the function. Fo

Strongly typed functional languages (including Reason) can often figure out a function's parameter types based on how the variables are used in the function. For example, given `(a, b) => a.push(b * 2)`, it could figure out that `b` must be of type `number` and `a` must be of type `Array<number>`, so the function author wouldn't need to write the type annotations. I think it's likely that TypeScript will never implement this (at least not at the level of sophistication of typical functional languages), given that it adds a lot of complexity to the language, and making types explicit at boundaries is usually good practice anyway.