Renaming "object safe" to "dyn compatible"

[Kajiih]

• I have searched open and closed issues and pull requests for duplicates, using these search terms:
  • ch18-3
  • object safe
  • dyn trait
• I have checked the latest main branch to see if this has already been fixed, in this file:
  • src/ch18-03-oo-design-patterns.md?plain=1#L360

URL to the section(s) of the book with this problem: https://rust-book.cs.brown.edu/ch18-03-oo-design-patterns.html

Description of the problem:

I noticed that the term "object safety" has been renamed to "dyn compatible" as per rust-lang/lang-team#286, but the book is not updated and still use the (confusing?) terms "object safe" and "object safety".

[...] however, this would violate object safety, because the trait doesn’t know what the concrete self will be exactly. We want to be able to use State as a trait object, so we need its methods to be object safe.

Tracking issue for this change: rust-lang/rust#130852

Suggested fix:

[...] however, this would violate dyn compatibility, because the trait doesn’t know what the concrete self will be exactly. We want to be able to use State as a trait object, so we need its methods to be compatible with trait objects-this is known as dyn compatible.

We might also add a reference to the former term, for example:

[...]-this is known as dyn compatible. In older documentation, this concept is often referred to as object safety.