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Specialize record field reads in method bodies; fix with-meta on symbols (#141)

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A protocol method reads its fields through the generic guarded keyword lookup
because the method's `this` param is untyped. defrecord now hints `this` with
the record type, the per-form inference seeds ^Record-hinted params (the
:fn branch previously typed all params :any — only the whole-program path
seeded phints), and run-passes feeds the inference the record shapes. So a
hinted param's field reads bare-index instead of going through the :jolt/type
tag guard.

This needed a with-meta fix: (with-meta sym ..) returned a proto'd table, so
symbol? was false and the macro-attached hint broke fn destructuring. Symbols
now carry metadata in-place in their struct (matching how the reader attaches
^hint), keeping symbol? true, as in Clojure.

Modest on dispatch (~3-5%): the field read is a small fraction of a dispatch;
the machinery (record-tag + protocol lookup + wrapper) dominates, which is the
inline-cache target (jolt-ez5h). But it's a correctness fix and lets any
^Record-hinted code — not just methods — drop the field-read guard per-form,
not only under whole-program.

Co-authored-by: Yogthos <yogthos@gmail.com>
This commit is contained in:
Dmitri Sotnikov 2026-06-16 15:14:59 +00:00 • committed by GitHub
parent 7d0b1d5695
commit 6772e28eae
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4 changed files with 32 additions and 6 deletions
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6
jolt-core/clojure/core/30-macros.clj
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@ -445,8 +445,12 @@
~@(map (fn [spec]
(let [argv (nth spec 1)
inst (first argv)
;; hint `this` with the record type so the inference
;; types it (jolt-3ko) and its field reads bare-index
;; instead of going through the runtime tag guard.
hinted (assoc argv 0 (vary-meta inst assoc :tag (name name-sym)))
binds (vec (mapcat (fn [f] [f `(get ~inst ~(keyword (name f)))]) fields))]
`(~(first spec) ~argv (let [~@binds] ~@(drop 2 spec)))))
`(~(first spec) ~hinted (let [~@binds] ~@(drop 2 spec)))))
specs)))]
`(do
;; deftype already defines ->name (= the ctor); no (name. …) interop needed,