Type aliasing

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.

C++ features type aliasing using the using keyword.

using Distance = int;

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

using Distance = int;

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

alias Distance = Int32;

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

alias Distance = int;

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

typedef Distance = int;

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

@type Distance :: integer

Elm features type aliasing using type alias.

type alias Distance = Int

F3 features type aliasing using the type keyword.

type Distance = int

Go features type aliasing using the type keyword and =.

type Distance = int

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

newtype Distance = int;

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

type Distance = Int;

Julia features type aliasing.^[8]

const Distance = Int

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

typealias Distance = Int

Nim features type aliasing.^[10]

type
  Distance* = int

OCaml features type aliasing.^[11]

type distance = int

Python features type aliasing.^[12]

Vector = list[float]

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 = list[float]

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

type Point = (u8, u8);

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

object Logarithms:
  opaque type Logarithm = Double

Swift features type aliasing using the typealias keyword.

typealias Distance = Int;

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

type Distance = number;

Zig features type aliasing by assigning a data type to a constant.^[16]

const distance = u32;