In Rust, I can make my function to accept a closure that is required to return an instance of some trait, say, Debug:

fn f(p: impl Fn(&str) -> Box<dyn Debug>) {}

Such function seems to work:

f(|b| Box::new("static")); //< works

However, it can't accept a closure that returns a value borrowed from the closure's argument:

f(|b| Box::new(b)); //< doesn't work

Neither it can accept a closure that returns a value borrowed from the outer context:

let a = &"a".to_owned();
// f(|b| Box::new(a)); //< doesn't work

I know how to make my function to be able to accept a closure that returns a value borrowed from the closure's argument:

fn f(p: impl for<'t> Fn(&'t str) -> Box<dyn 't + Debug>) {}
f(|b| Box::new("static")); //< works
f(|b| Box::new(b)); //< also works

However, such function still can't accept a closure that returns a value borrowed from the outer context.

Also, I know how to make my function to be able to accept a closure that returns a value borrowed from the outer context:

fn f<'t>(p: impl 't + Fn(&str) -> Box<dyn 't + Debug>) {}
f(|b| Box::new("static")); //< works
let a = &"a".to_owned();
f(|b| Box::new(a)); //< also works

However, such function can't accept a closure that returns a value borrowed from the closure's argument.

How can I write a function that is able to accept a closure that returns a value borrowed from the closure's argument, and is able to accept a closure that returns a value borrowed from the outer context, and is able to accept a closure that returns a value borrowed from both? E.g.:

fn f<???>(p: ???) {}
f(|b| Box::new("static")); //< must work
f(|b| Box::new(b)); //< must work too
let a = &"a".to_owned();
f(|b| Box::new(a)); //< must work too
f(|b| Box::new((a, b))); //< must work too

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