Type Aliases

A type alias introduces an additional name for an existing type using the type keyword:

type UserId = uint64;

An alias is transparent: it names the same type rather than creating a new one, so values move freely between the alias and the original without casts. UserId and uint64 are two spellings of one type, not two types.

What Can Be Aliased

Any type has a name, so any type can be aliased — primitives, arrays, pointers, and function types:

type UserId  = uint64;
type Vector3 = float32[3];
type Matrix4 = float32[4][4];
type Pointer = *uint8;
type Handler = func(x: int32, y: int32);

An alias is especially valuable for the longer forms — a nested array type or a function signature is far easier to read behind a single name.

Transparency

Because an alias is the same type as its target, no cast is ever needed to convert between them, in either direction:

let id: UserId = 1;
let raw: uint64 = id;     // OK — same type
let back: UserId = raw;   // OK — same type

This also means an alias provides no extra type checking: the compiler will not stop you from mixing a UserId with any other uint64. When you need a name the compiler keeps genuinely distinct, use a single-field struct instead.

Topics in This Chapter

Topic	Description
Using Type Aliases	Shortening signatures and documenting intent
Function Type Aliases	Naming callable signatures for callbacks
Built-in Aliases	Compiler-provided aliases such as float