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Type Aliases

Type aliases provide alternative names for existing types, simplifying complex type definitions.

info

This feature was added in v0.71.0.

Syntax​

type AliasName = ExistingType

Examples​

Basic Alias​

type Graph = map<string, string[]>

Alias Composition​

Type aliases can reference other aliases:

type Graph = map<string, string[]>
type DataStructure = string[] | Graph

Recursive Types​

Recursive type aliases are supported through map or list containers:

type JsonValue = int | string | bool | float | JsonObject | JsonArray
type JsonObject = map<string, JsonValue>
type JsonArray = JsonValue[]

Self-Referential Aliases​

Aliases can reference themselves through containers:

type JsonValue = int | float | bool | string | null | JsonValue[] | map<string, JsonValue>

Invalid Patterns​

Direct circular references without containers are invalid:

// Invalid - no value can satisfy this type
type A = B
type B = A

Use Cases​

Simplifying Complex Types​

// Without alias
function ProcessData(data: map<string, (int | string | bool)[]>) -> string { ... }

// With alias
type MixedArray = (int | string | bool)[]
type DataMap = map<string, MixedArray>
function ProcessData(data: DataMap) -> string { ... }

JSON-like Structures​

type Json = int | float | bool | string | null | Json[] | map<string, Json>

function ParseJson(input: string) -> Json {
    client "openai/gpt-4o"
    prompt #"
        Parse the following as JSON:
        {{ input }}
        {{ ctx.output_format }}
    "#
}

See Also​