Module spec 

IndexKind + IndexSpec — runtime declaration of a secondary index.

IndexSpec is the runtime declaration a Document type emits from Document::indexes() (#57); the on-disk reflection is the IndexDescriptor in crate::catalog. The spec is small and pure-data so it composes cleanly with the derive macro that lands in M9.

Power-of-ten posture

• Rule 5. IndexSpec::validate is the runtime boundary that pairs with the kind-specific type invariants (Composite requires ≥ 2 paths, Each requires exactly 1 path, etc.). The constructor helpers (IndexSpec::unique, ::each, …) call validate so a caller cannot construct an invalid spec.
• Rule 7. No unwrap / expect — every fallible path returns crate::Result.
• Rule 9. IndexKind is a concrete enum, NOT dyn IndexKind — static dispatch through match.

Structs

IndexSpec

A runtime index declaration.

Enums

IndexKind

What kind of secondary index a given IndexSpec declares.