rust-lang / rust-lang/rust-clippy

Politely mention that `Box<&T>` is almost the most useless type you can have

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@whirm is already working on this.

Since May 15, 2025.

A-lint good first issue T-middle
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Description

Found in the wild: https://stackoverflow.com/questions/48406077/mutation-of-a-variable-inside-while-loop

List of types that make no sense that we should be linting about:

  • Box<&T>
  • Box::new(SomeT) where sizeof::<T>() <= sizeof::<usize>()
    • unless there are Box::into_raw calls within the function
  • Rc<Box<T>>
  • Rc<Rc<T>>
  • Rc<&T>
  • more...?

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