[tialaramex]

The trick is that in Rust the implementer chooses which Traits to implement for their Class while in C++ the Concept chooses what properties it will require and then applies to any classes with matching properties whether that's desirable or not.

So in C++ the fact a Mouse is food::LovesCheese doesn't actually tell me whether the Mouse's programmer has any idea what it means to food::LovesCheese or whether the food::LovesCheese programmer knows about a Mouse. I need to carefully read the documentation, or the source code, or guess. It might be a complete accident, or at least an unlucky side effect.

In Rust the fact a Mouse has the trait food::LovesCheese always means specifically that either (1) the Mouse programmer explicitly implemented food::LovesCheese as part of a Mouse or (2) the food programmer explicitly implemented a way for Mouse to food::LovesCheese. Rust requires that nobody but them can do this, if I have a Mouse I got from somewhere but alas it doesn't food::LovesCheese and I wish it did, I need to build my own trivial wrapper type MyCheeseLovingMouse and implement the extra trait.

Either way as the user of any Mouse, you can be sure that the fact it has food::LovesCheese in Rust is on purpose and not just an unfortunate behaviour that nobody specifically intended and you need to watch out for.

[CodeMage]

Okay, now I understand what you meant. Concepts automatically "apply" to anything that satisfies them, whereas Rust traits have to be implemented deliberately.

Thank you for clarifying.