In what context and why is the 'non-Escaping' keyword used in Rust?

In Swift (not Rust), the keyword @noescape (before Swift 3) or the default behavior for closures is non-escaping closures, meaning closures that are guaranteed not to be stored or called after the function exits. In Rust, there is no specific keyword "non-Escaping," but there are similar ownership and borrowing concepts that ensure reference safety.

Regarding Swift, non-escaping closures are used for optimization and safety: the compiler knows that the closure will not outlive the function call, so it can avoid strong references and retain cycles.

Example in Swift:

func perform(action: () -> Void) { // non-escaping closure
    action()
}

Here, action cannot be stored or called later, simplifying memory management.

In Rust, lifetime management and borrowing are handled through the system of lifetimes and ownership, preventing references from "escaping" their scope.