When a data type has generic type parameters, it's not, strictly speaking, actually a data type at all. It is a whole family of data types. Let's look at Option for a moment. Option is defined as follows:
pub enum Option<T> {
None,
Some(T),
}
This means that it has one generic type parameter with the name T. If we try to use Option without specifying a type for that generic type parameter, Rust will report an error:
let x: Option = None;
It produces this error:
What that's telling us, in essence, is that Option isn't a usable data type. However, Option<u32> is, as is Option<String>, Option<Result<f64, String>>, and so on. Moreover, Option<u32> and Option<String> are not the same type, and Rust won't pretend that they are. They're two different data types that have the...
