struct Bar<'a> {
    items: Vec<&'a dyn Any>,
}

impl<'a> Bar<'a> {
    fn new() -> Self {
        Bar { items: Vec::new() }
    }

    fn add<T>(&mut self, item: &'a T) {
        self.items.push(item);
    }
}

the parameter type T may not live long enough
the parameter type T must be valid for the static lifetime…rustcClick for full compiler diagnostic
mod.rs(45, 13): consider adding an explicit lifetime bound: : 'static

I don’t understand why the type T requires a 'static lifetime. Now, I could argue that in some cases T may be some anonymous type such as a closure and as a result won’t have a static lifetime. Thinking this, I change the code slightly to put a lifetime bound on T as well.

struct Bar<'a> {
    items: Vec<&'a dyn Any>,
}

impl<'a> Bar<'a> {
    fn new() -> Self {
        Bar { items: Vec::new() }
    }

    fn add<T>(&mut self, item: &'a T) where T: 'a {
        self.items.push(item);
    }
}

This STILL results in the same error as above.