If you have a struct of type T and an instance of that struct t, you can create a new instance using the syntax

  T { ..t }

which means "a new T with all the fields set to their values in t".

Inside the trait "Self" is an alias for "Number".

"&self" is shorthand for "self: &Number", i.e., a reference to Number.

To dereference a reference, prefix with

  *

So:

  self

has type "&Number"

and

  *self

has type "Number".

Thus,

  Self { ..*self }

is creating a new instance of Number with its each set to the same value as self.

Disclaimer! everything I know about rust I learned 2 days ago from this blog post, so I might be wrong :-)