Implementing Drop Order in Rust

This challenge focuses on understanding and controlling the order in which Rust's destructors (or drop implementations) are called. This is crucial for managing resources like file handles, network connections, or memory, ensuring they are cleaned up predictably and safely, especially in complex scenarios involving nested data structures or custom resource management.

Problem Description

You need to implement a mechanism to precisely control the order in which a collection of Rust objects, each implementing the Drop trait, are deallocated. This is particularly important when the order of dropping matters, for example, when one object's cleanup might depend on another object still being available, or to prevent double-frees or resource leaks.

What needs to be achieved: Create a struct that holds multiple values of different types, all of which implement the Drop trait. You must then provide a way to explicitly trigger the dropping of these held values in a user-defined order.

Key Requirements:

Define several distinct types, each with a Drop implementation that logs a message indicating when it's being dropped and which value it holds.
Create a container struct that can hold instances of these distinct types.
Implement a method on the container struct that accepts a sequence (e.g., a Vec or slice) specifying the order in which the held items should be dropped.
When this method is called, the items in the container should be dropped according to the specified order, and their Drop implementations should be executed accordingly.
The container struct itself should also implement Drop, ensuring any remaining items are dropped when the container goes out of scope, but this should happen after the explicit drop order mechanism has completed.

Expected Behavior: The Drop messages for the held items should appear in the console output in the exact order specified by the drop order mechanism. If the container is dropped without explicitly calling the drop order method for all items, the remaining items should be dropped in their natural, LIFO (Last-In, First-Out) order relative to each other within the container.

Edge Cases to Consider:

Dropping items that have already been dropped.
Specifying an invalid item identifier for dropping.
The container holding fewer items than specified in the drop order.
The container holding more items than specified in the drop order, and what happens to the remaining items.

Examples

Example 1:

// Assume the following structs are defined:
struct ItemA { id: usize, value: String }
impl Drop for ItemA { fn drop(&mut self) { println!("Dropping ItemA with id: {} and value: {}", self.id, self.value); } }

struct ItemB { id: usize, value: i32 }
impl Drop for ItemB { fn drop(&mut self) { println!("Dropping ItemB with id: {} and value: {}", self.id, self.value); } }

// Container setup:
let mut container = Container::new();
container.add(ItemA { id: 1, value: "Alpha".to_string() });
container.add(ItemB { id: 2, value: 42 });
container.add(ItemA { id: 3, value: "Beta".to_string() });

// Explicit drop order:
container.drop_in_order(&[DropOrder::ItemA(1), DropOrder::ItemB(2)]);

// Expected Output:
// Dropping ItemA with id: 1 and value: Alpha
// Dropping ItemB with id: 2 and value: 42

// When 'container' goes out of scope (e.g., end of main function):
// Dropping ItemA with id: 3 and value: Beta

Example 2:

// Using the same ItemA and ItemB structs as above.

// Container setup:
let mut container = Container::new();
container.add(ItemB { id: 5, value: 100 });
container.add(ItemA { id: 4, value: "Gamma".to_string() });

// Explicit drop order:
container.drop_in_order(&[DropOrder::ItemA(4)]);

// Expected Output:
// Dropping ItemA with id: 4 and value: Gamma

// When 'container' goes out of scope:
// Dropping ItemB with id: 5 and value: 100

Example 3 (Invalid Identifier):

// Using the same ItemA and ItemB structs as above.

// Container setup:
let mut container = Container::new();
container.add(ItemA { id: 1, value: "Alpha".to_string() });
container.add(ItemB { id: 2, value: 42 });

// Explicit drop order:
// Trying to drop an item that doesn't exist or has already been dropped.
// The behavior here should be to ignore the invalid request and proceed.
container.drop_in_order(&[DropOrder::ItemA(99)]); // ItemA with id 99 does not exist.

// Expected Output:
// (No output from the invalid drop request)

// When 'container' goes out of scope:
// Dropping ItemA with id: 1 and value: Alpha
// Dropping ItemB with id: 2 and value: 42

Constraints

The solution should be implemented entirely in Rust.
The container should be able to hold at least 10 different items.
The drop order specification should allow for specifying which type and identifier of an item to drop.
The drop_in_order method should handle the case where an item to be dropped has already been dropped or doesn't exist gracefully (e.g., by doing nothing for that specific request).
Performance: The act of managing the drop order should not introduce significant overhead beyond what's necessary for tracking and dropping.

Notes

Consider how you will store the items within the container to allow for unique identification and retrieval for dropping. Box or Rc might be useful here.
Think about how to represent the order in which items should be dropped. An enum that variants for each item type is a common pattern.
The core challenge is about manual deallocation control and managing ownership when Rust's default dropping rules are overridden. You cannot simply call drop() directly as that would be a compile-time error. You need to manage the lifecycle of the objects within your container.
The Drop trait in Rust is implicitly called when a value goes out of scope. Your task is to simulate or trigger this behavior explicitly for a subset of items in a controlled sequence.