This would break the principle that you always know how to invoke a function by looking at its signature. Option of T and Result of T are not the same type as T

This would break the principle that you always know how to invoke a function by looking at its signature. Option of T and Result of T are not the same type as T. You would have to look at the body of the function, or rustdoc, to know how to invoke it, which would be very annoying. Besides, what is the error type for Result? You haven't declared it.