Function union

union<V extends { readonly [variant: string]: Lazy<ValueShape> }>(
    variants: V,
): Union<
    {
        readonly [K in string
        | number
        | symbol]: V[K] extends Lazy<S> ? S : never
    },
>
Creates a union of named value shapes.

Each key in the record serves as a type discriminator for polymorphic property values, enabling JSON-LD @container: @index patterns while preserving RDF semantics.

Unions are pure type discriminators — cardinality constraints are applied by wrapping the union in a Range via cardinality helpers like required, optional, etc.
Type Parameters
- V extends { readonly [variant: string]: Lazy<ValueShape> }
  The variants record type
Parameters
- variants: V
  Record mapping variant names to value shapes
Returns Union<
    {
        readonly [K in string
        | number
        | symbol]: V[K] extends Lazy<S> ? S : never
    },
>
A union with the specified variants
Example
```
const address = property(optional(union({
  string: string(),
  PostalAddress: PostalAddress
})));
```
See
- SHACL § 4.7.2 sh:or
- JSON-LD 1.1 § 4.6.1 Data Indexing
- Defined in resource.ts:1325