Had the same issue a few months ago.
The pointer can only be referenced by one variable at a time.
If you "move" the pointer from a to b then a is figuratively "used up" because a is now blocked from doing anything with the pointer anymore.
I guess, for Rust itself the pointer is still referenced by a, Rust just blocks you from using it. But thinking you moved it to another variable helped me a bit.
a = 2; b = a; c = a;
There's no pointer in there, just 2.
Someone needs to explicitly nail down the mission statement of Rust... because to me it seems to be
"Rust will introduce pointers where they don't need to be, and then try to protect you from the results with obsessive rules"
Hope it helps!
Maybe playing around with the code would help you better, because that last line doesn't make any sense: https://play.rust-lang.org/?version=stable&mode=debug&editio...
What '2 is Copy' means precisely that Rust WILL NOT 'introduce pointers where they don't need to be' - 2 is fine to 'alias' because it's a primitive type and so a copy is made when you do that, (i.e. the type implements the 'Copy' trait). However when you do that with complex types that do not implement Copy, you're moving ownership to the new variable so cannot use the old one any more.