// std::error

pub trait Error: Debug + Display {
    // existing API unchanged

    fn provide<'a>(&'a self, req: &mut Demand<'a>) {}
}

impl dyn Error + Send + Sync + 'static { // and all combinations of send/sync
    pub fn request_ref<T: ?Sized + 'static>(&self) -> Option<&T> {
        core::any::request_ref(self)
    }

    pub fn request_value<T: 'static>(&self) -> Option<T> {
        core::any::request_value(self)
    }
}