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One IRef seam: watches/validators/meta over atom, var, and agent

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add-watch/remove-watch/set-validator!/get-validator were atom-only; the
atom ctor ignored :meta and :validator; watching a var crashed. Now the
ARef contract is one seam: atoms keep their record slots (hot path
unchanged), every other reference type registers a predicate and stores
watches/validators in identity-keyed side tables, and notifies at its
mutation points. Vars notify on root changes (def on a watched var,
var-set outside a thread binding, alter-var-root — thread-binding sets
don't notify, like the JVM); agents notify per action. The def-var! wrap
costs two weak-table probes per def and does IRef work only on a watched
var.

Ctor options follow ARef: the validator gates the initial value
(IllegalStateException 'Invalid reference state' — also the class for
rejected swap!/reset!), :meta must be a map (else ClassCastException),
nil allowed. meta reads any reference through the identity side-table
(the type-gated fall-through is gone); alter-meta!/reset-meta! work on
non-var references.

Runtime-only (no re-mint). 9 JVM-certified corpus rows; spec entry; cts
baseline 5781 -> 5805 pass, 73 baselined namespaces (the residual error
in the watch namespaces is their STM ref section — refs stay out of
scope).
This commit is contained in:
Yogthos 2026-07-02 09:07:00 -04:00
parent 257f822825
commit f80f9aab4b
8 changed files with 203 additions and 42 deletions
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6
host/chez/natives-meta.ss
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@ -27,9 +27,9 @@
;; so dispatch to its meta method rather than the identity side-table — which
;; the deftype's reconstructed instances would not share.
((and (jrec? x) (jrec-cl x "meta")) => (lambda (m) (jolt-invoke m x)))
((or (pvec? x) (pmap? x) (pset? x) (cseq? x) (empty-list-t? x) (jolt-lazyseq? x) (jrec? x) (jreify? x) (procedure? x))
(hashtable-ref meta-table x jolt-nil))
(else jolt-nil)))
;; everything else (collections, fns, reify, atoms/agents and any reference
;; type) reads the identity side-table; a value with no entry is nil meta.
(else (hashtable-ref meta-table x jolt-nil))))
;; fresh-identity copy of a metadatable value (so attaching meta doesn't mutate
;; the original). cseq/procedure can't be copied meaningfully — keyed in place.