What do you think about this new functionnality

[notriddle]

Is it possible to specialize HashMap Index for Copy types

The feature your asking for is just plain old function overloading, which Rust does not have. There are a few reasons I think its unlikely Rust will have this feature any time soon: It's not usually that useful, since you can just use a different method name. Using it is often not a great idea, because if these methods have different signatures and different implementations, like as not they should have a different name. In a language with a lot of type parameters flying around like Rust has, …