Type operators make type intent visible in code.

Annotation with `:`

Use : when a name, parameter, or return value needs an explicit type.

let port : Int := 8080;

let parsePort (text : String) : Int := 8080;

Annotations are useful at public boundaries and when inference would hide the intended shape.

Type test with `:?`

Use :? when code needs a Boolean answer about a value type.

let value := 42;
let isInt := value :? Int;

isInt is a Boolean. Testing does not change the value.

Use :?> when code must treat a value as a specific type.

let value := 42;
let number := value :?> Int;

A cast is stronger than a test. Prefer keeping values typed at the boundary so casts stay rare.

Use where when a generic function needs a capability or shape.

let requireSame[T, U] (value : T) : T where T ~= U := value;

Use constraints when a generic function needs a type relationship that callers must satisfy.