Rust Drops An Owned Value When its Owner Leaves Scope

A variable is valid from the point where it is defined until the end of its scope in source
Let’s understand this concept with an example walkthrough as well.

Curly braces can create a scope, let me show you what I mean by that:

fn main() {
	{
		let message = String::from("Server started");
		println!("{message}");
	}
	
	// `message` no longer exists here
}

The string message is created inside the inner block. As long as execution remains inside that block, we can use message but once the execution reaches the closing brace, message is dropped and its heap allocation is cleaned up. You’ll get an error if you try to run this:

fn main() {
	{
		let message = String::from("Server started");
		
	}
	
	println!("{message}");
}

Now, lets look at another scenario where you are returning an owned value from a function:

fn create_message() -> String {
    let message = String::from("Server started");
    message
}
 
fn main() {
    let message = create_message();
    println!("{message}");
}

The local variable inside create_message disappears when the function finishes but the String is not destroyed there. Ownership of the value is returned to the caller and stored in the new message variable