Type Aliases

C

// Since C89
// typedef creates an alias for an existing type.
typedef unsigned int uint;
typedef struct User User;

typedef struct Point
{
	int x;
	int y;
} Point;

uint id = 10;
Point point = { .x = 10, .y = 20 };

C++

// Option 1 - using (Since C++11)
using UserId = int;
using StringList = std::vector<std::string>;

// Option 2 - typedef
typedef int UserId;

UserId id {10};

C#

// File-scoped aliases
using UserId = System.Int32;
using UsersById = System.Collections.Generic.Dictionary<int, User>;

UserId id = 10;

Java

// No Native Support.
// Use a class, record (Since Java 16), interface, or generic type name to express the domain concept.

record UserId(int value) {}
UserId id = new UserId(10);

Rust

// Type alias
type UserId = u64;
type Result<T> = std::result::Result<T, std::io::Error>;

let id: UserId = 10;

// Newtype pattern when a distinct type is required
struct OrderId(u64);

Go

// Alias declaration (Since Go 1.9)
type UserID = int

// New defined type
type OrderID int

var userID UserID = 10
var orderID OrderID = 20

Javascript

// No Native Support.
// Javascript has no static type aliases.
// Use naming conventions, classes, or JSDoc when useful.

/** @typedef {number} UserId */
/** @type {UserId} */
const id = 10;

Typescript

type UserId = number;
type Point = {
	x: number;
	y: number;
};

type Result<T> = { ok: true; value: T } | { ok: false; error: Error };

const id: UserId = 10;

Python

from typing import TypeAlias

# TypeAlias is available from typing in Python 3.10+.
UserId: TypeAlias = int
Point: TypeAlias = tuple[int, int]

user_id: UserId = 10
point: Point = (10, 20)