Component is supposed to be implemented for Position by the derive macro. #[derive(Debug, Component, Clone, Copy)] basically means "generate an implementation of Debug, Component, Clone and Copy for the type below". But because there was an error cannot find derive macro Component in this scope, the implementation was not generated.
For me, simply importing the traits being used was enough to make it compile (I did not add specs-derive to Cargo.toml). use specs::{Component, VecStorage};