Lazy values scoped to object identity. Keys are weakly held; no enumeration,
size, or deterministic garbage-collection timing is exposed.
Factories run synchronously. Thrown failures are not cached; undefined is.
Promise values are stored as-is (including rejected promises).
Lazy values scoped to object identity. Keys are weakly held; no enumeration, size, or deterministic garbage-collection timing is exposed. Factories run synchronously. Thrown failures are not cached; undefined is. Promise values are stored as-is (including rejected promises).