Lint against passing &Box<dyn Any> to a function accepting &dyn Any

[Ralith]

What it does

Functions taking &dyn Any will accept any 'static argument. Passing a &Box<dyn Any> (or other smart pointer, or upcasting another trait object that implies Any) is therefore possible, but probably not intended.

Advantage

Probably the intended effect.

Drawbacks

In rare cases someone might do this on purpose, but that's weird enough to merit explicit documentation.

Example

let x: &Box<dyn Any>;
frob(x)

Could be written as:

let x: &Box<dyn Any>;
frob(&**x)

[Ralith]

@rustbot claim