Changing the rules of Rust

In Rust, there are certain API decisions about what is and isn’t sound that impact all Rust code. That is, a decision was made to allow or not allow types which have certain safety requirements, and now all users are committed to that decision. They can’t just use a different API with different rules: all APIs must conform to these rules. These rules are determined through certain “marker” traits. If a safe API could do something to a value of a type which some types don’t support, the API must ...