Mutable borrows are not shared - you can't touch the data elsewhere while it's borrowed mutably, and you can't get a mutable borrow while there's immutable borr

Mutable borrows are not shared - you can't touch the data elsewhere while it's borrowed mutably, and you can't get a mutable borrow while there's immutable borrows. Shared state is unfortunately a common affliction on large codebases, and if the language supports and even encourages it, it can be difficult to prevent it from happening as the codebase grows and customers want features that don't fit into the architecture wonderfully.