[constantcrying]

I explicitly excluded primitive types in my previous comment.

I have never seem a codebase where this was an issue. The most important concept in programming is defining your data structures. Professional programs almost never operate on primitive data structures, but always on larger structures, like classes or structs.

This is why this is only a problem for you. I don't want to be insulting, but you need to brush up on your data structures. The need to pass a modifiable data structure almost never arises, the idiom in your OP is extremely uncommon and would likely not pass any code review.

[constantcrying]

You don't need to wrap fields. You just pass the classes.

Think about why nobody but you is inconvenienced by this. I am sorry, this is a you problem, because you are violating common idioms of the language.

There is basically never a reason not to pass your data structure to a function, which is why what you are doing is an incredibly niche functionality.

Also functions should be particular to data structure. That is why types exists.

[the__alchemist]

General functions are useful.

It is not a me problem, which is why Rust has fixed this. You are arguing that functions which mutate parameters generally are not useful, which isn't true. You have implied that I have a lack of knowledge of data structures, my code wouldn't pass code review. Reflect: You are proposing it is preferable to have a simple function accept a whole data structure when it may only act on one or more of its fields, and may be used in other places. That is a semantic misdirection, and provincialization.

[the__alchemist]

You have missed the point: Functions should not need to be provincial to a specific data structure. Nor should data structures include field wrappers to subvert a language's sloppy mutation semantics.

The point is that with mutable references, you can modify only the part of the struct you need to, using a general function. You can use this same function to modify a different part of the structure, or a different structure, or a free variable.

Your inference that preferring mutable references to wrapper structs implies insufficient knowledge of data structures is puzzling and incorrect.