Add an opaque `Set` newtype paralleling `Object`, living under
`src/value/set/` with the same module structure (`mod.rs` /
`iter.rs` / `serde.rs`). `Set` wraps `BTreeSet<Value>` today but
exposes only a curated surface: `contains`, `insert`, `remove`,
`iter`, `iter_sorted`, `cursor` (resumable), `is_subset`,
`intersection`, `difference`, serde, and a hand-written `Ord`.
The cursor types are re-exported behind the `rvm` feature so the
follow-up `IterationState::Set` swap can land additively.
To free the `Set` name for the new public type, the crate-internal
`BTreeSet as Set` / `HashSet as Set` aliases in `lib.rs` are
renamed to `MapSet`. All in-tree consumers of the old alias are
updated in lockstep.
`Value::Set` is unchanged in this commit (still wraps
`Rc<BTreeSet<Value>>`); the payload swap and call-site migration
ship in the next PR.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Add an opaque Object type for the key→value storage backing
Value::Object. It exposes a small set of methods (get, insert, remove,
iter, iter_sorted, cursor, serde) and keeps the backing store private,
so future representations -- inline small-map, hash-backed, lazy,
arena, FFI-callback -- can plug in without touching the call sites
that name this type.
Nothing in the engine uses Object yet. Value::Object still wraps
Rc<BTreeMap<Value, Value>>; the payload swap and call-site migration
come in the next PR. Object stands on its own unit tests in the
meantime.
docs/value/object.md walks through the design, the precedents it
follows (serde_json::Map, toml::Table, simdjson DOM), and the
concrete workloads the abstraction is meant to unlock.
A matching Set abstraction follows in a separate PR.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
