Builds on the ^:struct keyword-lookup hint:
- ^TypeName for records. A tag naming a defrecord/deftype now resolves to the
struct fast path: record instances are tables tagged :jolt/deftype (not
:jolt/type), so a raw keyword get is correct for them. A new host contract fn
record-type? detects a record by its ->Name constructor; a non-record tag
(^String, ^long, ...) is ignored, as before.
- (get m :k) and (get m :k default) now get the same inlined keyword lookup as
(:k m): the representation guard fast path when unhinted, and the bare get
when the subject is ^:struct/^Record. A variable/number/string key still
falls through to core-get. The two call shapes share one emitter
(emit-kw-lookup).
- JOLT_CHECK_HINTS=1 turns a violated hint into a clear runtime error (naming
the local and key) by keeping the guard and throwing on the tagged arm. It is
off by default with zero cost to normal builds (a hinted lookup still emits a
bare get), and is part of the image-cache fingerprint. This is the answer to
"a lying hint is silent": opt into checking during development.
- Docs: RFC 0004 records the design, soundness contract, and measurements; the
reader spec gains S12b (hints are semantically transparent; jolt recognizes
^:struct and ^Record as lookup-optimization assertions).
There is no Clojure keyword equivalent for "plain map / fast keyword access"
(Clojure hints are class names), so ^:struct stays a jolt-specific flag,
analogous to ^:dynamic.
Verified: conformance 335/335 in all three modes and the full jpm test pass; a
seeded ray-tracer render is byte-identical hinted vs unhinted; the struct-hint
test covers record hints, the get-form, inline propagation, and the checked-mode
error. Full render with hints holds at 13.3s -> 10.9s (1.22x).
#inst (jolt-rnh): an instant is an immutable tagged struct
{:jolt/type :jolt/inst :ms <epoch-millis>} — equality and map-key hashing by
INSTANT, so different offsets denoting the same moment are =. The reader
parses RFC3339 with Clojure's partial-timestamp defaults (#inst "2020" is
2020-01-01T00:00:00.000Z) and errors on malformed input; inst?/inst-ms in
the overlay; pr-str prints the canonical
#inst "yyyy-MM-ddThh:mm:ss.fff-00:00" and round-trips; str gives the bare
RFC3339 string. Self-evaluating in the evaluator (like uuid/chars).
Syntax-quote (jolt-l2a): a syntax-quoted self-evaluating literal (string,
number, boolean, nil, keyword, char) collapses to the literal at READ time,
matching Clojure's reader — so nested/adjacent backticks over literals are
inert: (= "meow" ```"meow") is true (jank pass-adjacent). Symbols still
qualify and collections still template. General nested syntax-quote over
non-literals remains UNVERIFIED in spec S25.
Tests: inst-spec (18 cases incl. partial defaults, offsets, round-trip),
+10 literal-collapse reader rows, +5 conformance rows (321x3). Spec
02-reader S20/S25 updated to normative. Suite stable 4470/86.
jolt no longer satisfies :clj in reader conditionals. The shortcut was a
measured net liability: :clj branches carry JVM interop and JVM-specific
test expectations jolt fails, and they shadowed :default branches jolt
passes. A/B over the suite: clj,default = 4967 assertions / 4324 pass / 119
errors; jolt,default = 5069 / 4470 / 81 (+146 pass, -38 errors, +8 clean
files). Baselines raised to 4470/86.
Matching is now by CLAUSE order like Clojure — the first clause whose key is
in the feature set wins (#?(:default 5 :clj 6) is 5 everywhere); the old code
scanned for :clj first, then :default, regardless of position.
Foreign clj-targeted libraries are a property of the LOADING CONTEXT, not the
platform: reader-features-set! opts a load into a compatibility set, and the
SCI bootstrap/runtime tests load SCI under ["jolt" "clj" "default"] (its
.cljc selects implementations via :clj with no :jolt branches).
JOLT_FEATURES remains the process-wide override.
RFC 0002 records the decision with the measured data; spec 02-reader S18 is
now normative (clause order, documented feature set, per-context override).
Reader tests updated to the portable set + an opt-in round-trip.
The lexical-syntax chapter, granularity modeled on jank's 62-file
per-construct reader corpus: token grammar (whitespace/comments, collections
with read-time duplicate checks, numbers incl. the N/M tower question,
symbols/keywords incl. ::auto-resolution, strings/chars), the quote-family
sugars, the full #-dispatch catalog with normative entries (anonymous fn
%-derivation, discard composition, reader conditionals, symbolic floats,
tagged literals), and the syntax-quote contract (core/alias/current-ns
qualification, template-stable gensyms, ~' idiom, distribution through
collections).
Adapting the corpus surfaced and filed three findings, recorded as labeled
divergences/UNVERIFIED in the chapter: nested syntax-quote doesn't collapse
(S25, (= "meow" ```"meow") is false), #inst reads as a bare string (identity
data reader, no instant type), and jolt satisfies :clj in reader
conditionals (feature-key policy under review).
reader-forms-spec gains 11 chapter-cited rows (discard stacking, ##Inf/
##-Inf/##NaN, :default conditionals, qualified var-quote identity, gensym
stability within vs across templates) — all passing.
