Type aliasing is a feature in some programming languages that allows creating a reference to a type using another name. It does not create a new type hence does not increase type safety. It can be used to shorten a long name. Languages allowing type aliasing include: C++, C# Crystal, D, Dart, Elixir, Elm, F#, Go, Hack, Haskell, Julia, Kotlin, Nim, OCaml, Python, Rust, Scala, Swift and TypeScript.

Example

C++

C++ features type aliasing using the using keyword.

using Distance = int;

C#

C# since version 12 features type aliasing using the using keyword. ^[1]

using Distance = int;

Crystal

Crystal features type aliasing using the alias keyword. ^[2]

alias Distance = Int32;

D

D features type aliasing using the alias keyword. ^[3]

alias Distance = int;

Dart

Dart features type aliasing using the typedef keyword. ^[4]

typedef Distance = int;

Elixir

Elixir features type aliasing using @type. ^[5]

@type Distance :: integer

Elm

Elm features type aliasing using type alias.

type alias Distance = Int

F#

F3 features type aliasing using the type keyword.

type Distance = int

Go

Go features type aliasing using the type keyword.

type Distance int

Hack

Hack features type aliasing using the newtype keyword. ^[6]

newtype Distance = int;

Haskell

Haskell features type aliasing using the type keyword. ^[7]

type Distance = Int;

Julia

Julia features type aliasing. ^[8]

const Distance = Int

Kotlin

Kotlin features type aliasing using the typealias keyword. ^[9]

typealias Distance = Int

Nim

Nim features type aliasing. ^[10]

type
  Distance* = int

OCaml

OCaml features type aliasing. ^[11]

type distance = int

Python

Python features type aliasing. ^[12]

Vector = listfloat

Type aliases may be marked with TypeAlias to make it explicit that the statement is a type alias declaration, not a normal variable assignment.

from typing import TypeAlias

Vector: TypeAlias = listfloat

Rust

Rust features type aliasing using the type keyword. ^[13]

type Point = (u8, u8);

Scala

Scala can create type aliases using opaque types. ^[14]

object Logarithms:
  opaque type Logarithm = Double

Swift

Swift features type aliasing using the typealias keyword.

typealias Distance = Int;

TypeScript

TypeScript features type aliasing using the type keyword. ^[15]

type Distance = number;

References