Crate lifetime

This crate provides traits and derive macros to change the lifetime of a type, allowing efficient reuse of your stucts or enums with any lifetime requirement.

macros feature

This crate’s macros are not enabled by default. Use the following in your Cargo.toml, replacing x.y with the version you want, to enable macros.

[dependencies]
lifetime = { version = "x.y", features = ["macros"] }

no_std

Use the following in your Cargo.toml, replacing x.y with the version you want, to disable the default std and alloc features.

[dependencies]
lifetime = { version = "x.y", default-features = false }

Examples

Note that the examples use explicit types and lifetimes to be more illustrative. Typically the lifetimes and/or types can be inferred by the compiler.

use lifetime::{IntoStatic, ToBorrowed};
use std::borrow::Cow;

let alice: Cow<'static, str> = Cow::Borrowed("Alice");

let borrowed_alice: Cow<'_, str> = alice.to_borrowed();
assert_eq!(borrowed_alice, alice);

let static_alice: Cow<'static, str> = borrowed_alice.into_static();
assert_eq!(static_alice, alice);

Here’s an example with a struct using the derive macros. The macros feature needs to be enabled.

use lifetime::{IntoStatic, ToBorrowed};
use std::borrow::Cow;

#[derive(IntoStatic, ToBorrowed)]
struct Header<'a> {
    name: Cow<'a, str>,
    value: Cow<'a, str>,
}

let xml: Header<'static> = Header {
    name: "content".into(),
    value: "xml".into(),
};
let mut xml_or_json: Header<'_> = xml.to_borrowed();
xml_or_json.value += " or json"; // creates a new String

assert_eq!(xml.value, "xml"); // xml header has not moved
assert_eq!(xml_or_json.value, "xml or json");

// IntoStatic converts all borrowed `&str` into `String`
let static_xml_or_json: Header<'static> = xml_or_json.into_static();
assert_eq!(static_xml_or_json.value, "xml or json");

Traits

IntoStatic

A trait for upgrading the lifetime of a type.

ToBorrowed

A trait for downgrading the lifetime of a type.

Derive Macros

IntoStatic

Derive macro generating an impl of the trait IntoStatic.

ToBorrowed

Derive macro generating an impl of the trait ToBorrowed.