Clone

The Clone macro generates a clone() method for deep copying objects. This is analogous to Rust’s Clone trait, providing a way to create independent copies of values.

Generated Output

Type	Generated Code	Description
Class	`classNameClone(value)` + `static clone(value)`	Standalone function + static wrapper method
Enum	`enumNameClone(value): EnumName`	Standalone function (enums are primitives, returns value as-is)
Interface	`ifaceNameClone(value): InterfaceName`	Standalone function creating a new object literal
Type Alias	`typeNameClone(value): TypeName`	Standalone function cloning by the alias’s shape

Names use camelCase conversion (e.g., Point -> pointClone).

Cloning Strategy

The generated clone dispatches on each field’s declared type, and a clone always equals its source under the derived PartialEq:

Primitives (string, number, boolean, bigint): Copied by value
Date, RegExp, URL, typed arrays: Copied by value
Arrays, Map, Set: Rebuilt, each element cloned by its own type (a map’s keys are shared, since lookups match them by identity)
Objects with @derive(Clone): Their standalone clone function
Optional fields: null/undefined pass through, and an absent optional field stays absent
Anything else (unions, object literals, unresolved types): structuralClone from @macroforge/core/structural

Example

Before (Your Code)

/** @derive(Clone) */
class Point {
    x: number;
    y: number;
}

After (Generated)

class Point {
    x: number;
    y: number;

    static clone(value: Point): Point {
        return pointClone(value);
    }
}

export function pointClone(value: Point): Point {
    const cloned = Object.create(Object.getPrototypeOf(value));
    cloned.x = value.x;
    cloned.y = value.y;
    return cloned;
}

Implementation Notes

Classes: Uses Object.create(Object.getPrototypeOf(value)) to preserve the prototype chain, ensuring instanceof checks work correctly
Enums: Simply returns the value (enums are primitives in TypeScript)
Interfaces/Type Aliases: An object literal copying each field for object types, element by element for fixed tuples, and structuralClone for unions and other shapes