Why ternary operator in swift is so picky?

Question

The question is very simple, but I just could not find the answer!

Why doesn\'t

return x == 0? \"\" : \"Hello\"

compile but

Answer 1

I think it has something to do with optionals.

It does. The documentation on operators says:

There is one caveat to the rules [regarding whitespace around operators]. If the ! or ? predefined operator has no whitespace on the left, it is treated as a postfix operator, regardless of whether it has whitespace on the right. To use the ? as the optional-chaining operator, it must not have whitespace on the left. To use it in the ternary conditional (? :) operator, it must have whitespace around both sides.