Option Values

Introduction

This proposal adds a standard Option union type to model values that may be
present or absent, plus syntactic sugar for optional chaining and defaults.

Motivation

Zirric currently relies on ad-hoc conventions for missing values. A canonical
Option type helps communicate intent and enables tooling to recognize optional
flows consistently.

Proposed Solution

Define an Option union with Some and None variants and a marker attribute
that enables optional operators.

@AnyOption()
union Option {
  data Some { value }
  data None
}

@Returns(User?)
fn findUser(id) {
  // returns Some(User) or None
}

let name = findUser(42)?.value.name ?? "Unknown"

Syntactic Sugar

• option?.value maps to Some(value) or None.
• option ?? "default" unwraps Some.value or returns the default for None.
• @String? expands to @Type(Option) @SomeType(String).

Detailed Design

• Option is a union with Some and None data variants.
• @AnyOption opt-in enables the ?. and ?? operators for option values.
• @SomeType provides a type hint for Some.value.

For the ??, ?. operators, the VM needs to look if the value is a @prelude.None.
If it is None, it should return the default value for ?? or skip the member access for ?..
In case of ?. the value will be wrapped into prelude.Some if needed if it is not prelude.None.

The goal is to support strongly typed optional types like PersonOption.

attr AnyOption {}

union Option {
	data Some {
		value
	}

	data None
}

attr SomeType {
	@Type(AnyType) type
}

Changes to the Standard Library

• Add @AnyOption, Option, and @SomeType in future/prelude.

Alternatives Considered

• Using null or none literals without a type wrapper, which makes optional
  flows implicit and harder to check.
• Reusing Result for optional values, which conflates absence with failure.

Acknowledgements

• Influenced by Swift’s Optional and Rust’s Option<T>.