> we cannot just require all generic parameters to be Clone, as we cannot assume they are used in such a way that requires them to be cloned.
No, this is backwards. We have to require all generic parameters are Clone, as we cannot assume that any are not used in a way that requires them to be Clone.
> The reason this is the way it is is probably because Rust's type system wasn't powerful enough for this to be implemented back in the pre-1.0 days. Or it was just a simple oversight that got stabilized.
The type system can't know whether you call `T::clone()` in a method somewhere.
No, this is backwards. We have to require all generic parameters are Clone, as we cannot assume that any are not used in a way that requires them to be Clone.
> The reason this is the way it is is probably because Rust's type system wasn't powerful enough for this to be implemented back in the pre-1.0 days. Or it was just a simple oversight that got stabilized.
The type system can't know whether you call `T::clone()` in a method somewhere.