It can be safe if the language provides a mechanism to tell the compiler that borrow_field1() and borrow_field2() will never mutably borrow the same fields. Thi

It can be safe if the language provides a mechanism to tell the compiler that borrow_field1() and borrow_field2() will never mutably borrow the same fields. This would be part of the public API of those functions, and compilation would fail if the implementations were changed to borrow the same fields.