Chez Phase 3 inc6a: zero-Janet spine (analyzer + emitter on Chez), macro-free

Cross-compile jolt.ir + jolt.analyzer + jolt.backend-scheme to Scheme def-var!
forms via the existing Janet emit pipeline (driver/emit-compiler-image) and run
them ON CHEZ over a Scheme jolt.host impl. A macro-free Clojure expression now
compiles and runs with no Janet in the loop: read (reader.ss) -> analyze
(jolt.analyzer on Chez) -> IR -> emit (jolt.backend-scheme on Chez) -> eval.

host/chez/host-contract.ss is the jolt.host contract on Chez (the portable seam
the cross-compiled analyzer/emitter call): form-* over the Chez reader's forms,
resolve-global/compile-ns/host-intern!/late-bind? over the var-cell registry. ctx
is an opaque record carrying the compile ns. Native-op names are declare-var!'d
into clojure.core so +, *, <, ... classify as :var and the emitter's native-op
path lowers them. form-macro? is a #f stub and macro expansion / syntax-quote /
record hints are stubs for inc6b (runtime macros, jolt-r8ku).

host/chez/compile-eval.ss is the spine entry (read-string -> analyze -> emit ->
eval). driver gains emit-compiler-image / ensure-compiler-image (image caching)
and program-zero-janet / eval-zero-janet.

Two bugs fixed in the keeper, not reproduced:
- the Chez reader stores an unqualified symbol's ns as #f, but the analyzer tests
  (nil? ns); hc-sym-ns normalizes #f/'() -> jolt-nil. Without it every handled
  special (if/do/fn*) misanalyzed as a plain invoke.
- char (int->char) was missing from clojure.core on Chez; the emitter's
  chez-str-lit needs it for keyword/string consts. Added jolt-char to converters.ss.

Gate: test/chez/spine-test.janet 15/15 (Chez-hosted analyzer value == Janet-hosted
oracle through the same emitter/RT; only the analysis host differs). Full Janet
gate green (150 files). driver.janet is in the prelude fingerprint so the cache key
moved; prelude content is unchanged. jolt-chez fingerprint/ensure-prelude made
public for the test harness.

host/chez/compile-eval.ss

@@ -0,0 +1,28 @@
+;; compile-eval.ss (jolt-hs9n, Phase 3 inc6) — the zero-Janet compile spine.
+;;
+;; Ties together the cross-compiled compiler image (jolt.ir + jolt.analyzer +
+;; jolt.backend-scheme, loaded as def-var! forms) and the host contract
+;; (host-contract.ss) into a runtime entry: a Clojure source string is read by the
+;; Chez data reader, analyzed by the ON-CHEZ analyzer to IR, emitted to Scheme by
+;; the ON-CHEZ emitter, and eval'd — no Janet in the loop. This is the spine the
+;; stage2==stage3 bootstrap fixpoint (later increments) closes over.
+;;
+;; Loaded after host-contract.ss + the compiler image.
+
+(define jolt-ce-analyze (var-deref "jolt.analyzer" "analyze"))
+(define jolt-ce-emit (var-deref "jolt.backend-scheme" "emit"))
+(define jolt-ce-read (var-deref "clojure.core" "read-string"))
+
+;; Source string -> Scheme source string (read -> analyze -> emit, all on Chez).
+;; `ns` is the compile namespace unqualified symbols resolve against.
+(define (jolt-analyze-emit src ns)
+  (let* ((form (jolt-ce-read src))
+         (ctx (make-analyze-ctx ns))
+         (ir (jolt-ce-analyze ctx form)))
+    (jolt-ce-emit ir)))
+
+;; Source string -> value (compile on Chez, then eval the emitted Scheme in the
+;; top-level environment where rt.ss's runtime procedures live).
+(define (jolt-compile-eval src ns)
+  (eval (read (open-input-string (jolt-analyze-emit src ns)))
+        (interaction-environment)))

host/chez/converters.ss

@@ -121,6 +121,11 @@
 (def-var! "clojure.core" "symbol" jolt-symbol-new)
 (def-var! "clojure.core" "gensym" jolt-gensym)
 (def-var! "clojure.core" "int" jolt-int)
+;; char: coerce a code point (jolt's all-flonum number) to a Chez char; pass a
+;; char through. Inverse of int on chars. (Missing on Chez before jolt-hs9n — the
+;; cross-compiled emitter's chez-str-lit needs it for printable-ASCII escaping.)
+(define (jolt-char x) (if (char? x) x (integer->char (exact (round x)))))
+(def-var! "clojure.core" "char" jolt-char)
 ;; long: same truncation as int in jolt's all-flonum model (seed core-long =
 ;; math/trunc; char -> code point). Distinct cell so (long ...) resolves.
 (def-var! "clojure.core" "long" jolt-int)

host/chez/driver.janet

@@ -229,6 +229,101 @@
   (cset-prelude! ctx false)
   [(string/join out "\n") emitted total])
 
+# --- analyzer/emitter cross-compile (jolt-hs9n, the zero-Janet spine) ---------
+# Phase 3 inc6: cross-compile the PORTABLE compiler (jolt.ir + jolt.analyzer +
+# jolt.backend-scheme) to Scheme def-var! forms so analyze->IR->emit runs ON CHEZ.
+# Same emit pipeline as the core prelude, but for jolt-core/jolt/* namespaces
+# rather than clojure.core: jolt.* refs lower to var-deref (the prelude-mode gate
+# only rejects clojure.* refs), clojure.core refs resolve from the loaded prelude,
+# and the jolt.host form-*/resolve-global/... refs resolve from host-contract.ss.
+
+(defn- emit-ns-forms-list
+  "Cross-compile one namespace's source to a list of guard-wrapped def-var! Scheme
+  strings (prelude mode must already be ON). Registers the ns' requires/aliases in
+  ctx first so cross-ns refs resolve at emit time; skips ns + macro forms (macros
+  are analyze-time only, already expanded at their use sites)."
+  [ctx ns-name src]
+  (tctx/create-ns ctx ns-name)
+  (tctx/ctx-set-current-ns ctx ns-name)
+  (def out @[])
+  (each f (parse-all src)
+    (def ns-form? (and (indexed? f) (> (length f) 0) (= "ns" (sym-name (in f 0)))))
+    (if ns-form? (protect (api/eval-one ctx f)) (scan-eval-requires! ctx f))
+    (unless (or ns-form? (macro-form? f))
+      (def res (protect (cemit ctx (backend/analyze-form ctx f))))
+      (when (res 0)
+        (array/push out (string "(guard (e (#t #f))\n  " (res 1) ")")))))
+  out)
+
+(def compiler-ns-files
+  [["jolt.ir" "jolt-core/jolt/ir.clj"]
+   ["jolt.analyzer" "jolt-core/jolt/analyzer.clj"]
+   ["jolt.backend-scheme" "jolt-core/jolt/backend_scheme.clj"]])
+
+(defn emit-compiler-image
+  "Cross-compile the analyzer pipeline (jolt.ir + jolt.analyzer +
+  jolt.backend-scheme) to a Scheme string of prelude-mode def-var! forms — the
+  analyze->IR->emit spine running ON CHEZ (jolt-hs9n). Load AFTER rt.ss +
+  host-contract.ss + the core prelude. Returns [scheme total]."
+  [ctx]
+  (ensure-clj-emitter ctx)
+  # ensure-analyzer is lazy; a trivial analyze builds jolt.ir/jolt.analyzer/
+  # jolt.passes in the Janet ctx so their vars resolve while we emit their source.
+  (protect (backend/analyze-form ctx (in (r/parse-next "nil") 0)))
+  (cset-prelude! ctx true)
+  (def prev-ns (tctx/ctx-current-ns ctx))
+  (def out @[])
+  (each [ns-name path] compiler-ns-files
+    (array/concat out (emit-ns-forms-list ctx ns-name (slurp path))))
+  (tctx/ctx-set-current-ns ctx prev-ns)
+  (cset-prelude! ctx false)
+  [(string/join out "\n") (length out)])
+
+(defn ensure-compiler-image
+  "Build (once) and return the path to the cross-compiled compiler image — the
+  jolt.ir/jolt.analyzer/jolt.backend-scheme def-var! forms (jolt-hs9n). Cached on
+  disk keyed by the same fingerprint scheme as the prelude; pass an explicit path
+  to control caching from the test harness."
+  [ctx path]
+  (unless (os/stat path)
+    (def [img _] (emit-compiler-image ctx))
+    (spit path img))
+  path)
+
+(defn program-zero-janet
+  "Assemble a fully self-hosted Chez program: rt.ss + the core prelude +
+  host-contract.ss + the cross-compiled compiler image + compile-eval.ss, then
+  compile AND eval `src` ON CHEZ (read->analyze->emit->eval, no Janet). The
+  zero-Janet spine (jolt-hs9n)."
+  [prelude-path image-path src ns]
+  (string
+    "(import (chezscheme))\n"
+    "(load \"host/chez/rt.ss\")\n"
+    "(set-chez-ns! \"clojure.core\")\n"
+    "(load " (string/format "%j" prelude-path) ")\n"
+    "(load \"host/chez/post-prelude.ss\")\n"
+    "(set-chez-ns! \"user\")\n"
+    "(load \"host/chez/host-contract.ss\")\n"
+    "(load " (string/format "%j" image-path) ")\n"
+    "(load \"host/chez/compile-eval.ss\")\n"
+    "(printf \"~a\\n\" (jolt-final-str (jolt-compile-eval "
+    (string/format "%j" src) " " (string/format "%j" ns) ")))\n"))
+
+(defn eval-zero-janet
+  "Compile+run `src` through the ON-CHEZ analyzer/emitter (zero Janet). Needs a
+  prebuilt core prelude (`prelude-path`) and compiler image (`image-path`).
+  Returns [code stdout stderr]."
+  [prelude-path image-path src &opt ns scheme-out]
+  (default ns "user")
+  (def prog (program-zero-janet prelude-path image-path src ns))
+  (def path (or scheme-out (string "/tmp/jolt-zero-janet-" (os/getpid) ".ss")))
+  (spit path prog)
+  (def proc (os/spawn ["chez" "--script" path] :p {:out :pipe :err :pipe}))
+  (def out (drain (proc :out)))
+  (def err (drain (proc :err)))
+  (def code (os/proc-wait proc))
+  [code (string/trim out) (string/trim err)])
+
 (defn program-with-prelude
   "Assemble a runnable Chez program that loads rt.ss, loads the assembled core
   prelude from `prelude-path` (a file written once), then prints `final-scm`."

host/chez/host-contract.ss

@@ -0,0 +1,197 @@
+;; host-contract.ss (jolt-hs9n, Phase 3 inc6) — the jolt.host contract on Chez.
+;;
+;; The portable seam between jolt-core (analyzer/IR/emitter, cross-compiled to
+;; Scheme) and the host. Mirrors src/jolt/host_iface.janet's `exports`: every
+;; contract fn is def-var!'d into the "jolt.host" namespace so the cross-compiled
+;; jolt.analyzer / jolt.backend-scheme — whose unqualified form-*/resolve-global/
+;; ... refs lower to (var-deref "jolt.host" ...) — resolve here at runtime.
+;;
+;; This is what puts analyze->IR->emit ON CHEZ (the zero-Janet spine). It runs
+;; over the Chez data reader's forms (reader.ss): symbols are symbol-t, lists are
+;; cseq (list?), () is empty-list-t, vectors/maps are pvec/pmap, sets and #tag/
+;; regex/inst/uuid are pmaps tagged :jolt/type, chars are NATIVE Chez chars.
+;;
+;; Loaded after rt.ss + reader.ss + the core prelude; before the compiler image.
+
+;; --- the analyze ctx --------------------------------------------------------
+;; ctx is opaque to the analyzer (only ever threaded to these contract fns); we
+;; make it a box carrying the compile namespace. The var/ns registry it consults
+;; is the global var-table (rt.ss).
+(define-record-type chez-actx (fields (mutable cns)) (nongenerative chez-actx-v1))
+(define (make-analyze-ctx ns) (make-chez-actx ns))
+
+;; Interned keywords reused for form tags + resolve-global's result map.
+(define hc-kw-jolt-type (keyword "jolt" "type"))
+(define hc-kw-jolt-set  (keyword "jolt" "set"))
+(define hc-kw-jolt-tagged (keyword "jolt" "tagged"))
+(define hc-kw-value (keyword #f "value"))
+(define hc-kw-tag   (keyword #f "tag"))
+(define hc-kw-form  (keyword #f "form"))
+(define hc-kw-kind  (keyword #f "kind"))
+(define hc-kw-ns    (keyword #f "ns"))
+(define hc-kw-name  (keyword #f "name"))
+(define hc-kw-var   (keyword #f "var"))
+(define hc-kw-unresolved (keyword #f "unresolved"))
+(define hc-kw-regex (keyword #f "regex"))
+(define hc-kw-inst  (keyword #f "#inst"))
+(define hc-kw-uuid  (keyword #f "#uuid"))
+
+;; --- form predicates --------------------------------------------------------
+(define (hc-sym? x) (symbol-t? x))
+(define (hc-list? x) (or (empty-list-t? x) (and (cseq? x) (cseq-list? x))))
+(define (hc-vec? x) (pvec? x))
+(define (hc-map? x) (and (pmap? x) (jolt-nil? (jolt-get x hc-kw-jolt-type))))
+(define (hc-set? x) (and (pmap? x) (eq? (jolt-get x hc-kw-jolt-type) hc-kw-jolt-set)))
+(define (hc-char? x) (char? x))
+(define (hc-literal? x)
+  (or (jolt-nil? x) (boolean? x) (number? x) (string? x) (keyword-t? x) (char? x)))
+
+(define (hc-tagged-of x tag)
+  (and (pmap? x)
+       (eq? (jolt-get x hc-kw-jolt-type) hc-kw-jolt-tagged)
+       (eq? (jolt-get x hc-kw-tag) tag)))
+(define (hc-regex? x) (hc-tagged-of x hc-kw-regex))
+(define (hc-inst? x) (hc-tagged-of x hc-kw-inst))
+(define (hc-uuid? x) (hc-tagged-of x hc-kw-uuid))
+
+;; --- form accessors ---------------------------------------------------------
+(define (hc-sym-name x) (symbol-t-name x))
+;; The reader stores an unqualified symbol's ns inconsistently (#f, '(), or
+;; jolt-nil — see converters.ss). The contract is jolt-nil for unqualified (the
+;; analyzer tests (nil? ns)), so normalize; a real ns string passes through.
+(define (hc-sym-ns x)
+  (let ((ns (symbol-t-ns x)))
+    (if (and ns (not (jolt-nil? ns)) (not (null? ns))) ns jolt-nil)))
+(define (hc-sym-meta x)
+  (let ((m (symbol-t-meta x)))
+    (if (and m (not (jolt-nil? m)) (not (null? m))) m jolt-nil)))
+
+;; list items -> jolt vector (pvec); the analyzer mapv's over the result.
+(define (hc-elements x)
+  (cond ((empty-list-t? x) empty-pvec)
+        ((cseq? x) (make-pvec (list->vector (seq->list x))))
+        (else empty-pvec)))
+(define (hc-vec-items x) x)                 ; already a pvec
+(define (hc-set-items x) (jolt-get x hc-kw-value))
+(define (hc-map-pairs x)
+  (let loop ((ks (if (jolt-nil? (jolt-seq (jolt-keys x))) '()
+                     (seq->list (jolt-seq (jolt-keys x))))) (acc '()))
+    (if (null? ks) (apply jolt-vector (reverse acc))
+        (loop (cdr ks) (cons (jolt-vector (car ks) (jolt-get x (car ks))) acc)))))
+(define (hc-regex-source x) (jolt-get x hc-kw-form))
+(define (hc-inst-source x) (jolt-get x hc-kw-form))
+(define (hc-uuid-source x) (jolt-get x hc-kw-form))
+
+;; The Chez reader does not record source offsets yet (jolt-q2kg).
+(define (hc-form-position x) jolt-nil)
+
+;; --- special forms ----------------------------------------------------------
+;; Mirrors host_iface special-names + interop-head? — forms the analyzer marks
+;; uncompilable (the handled specials are dispatched in analyze-list BEFORE this).
+(define hc-special-names
+  '("quote" "syntax-quote" "unquote" "unquote-splicing" "do" "if" "def"
+    "defmacro" "fn*" "let*" "loop*" "recur" "throw" "try" "set!" "eval" "new"
+    "." "gen-class" "monitor-enter" "monitor-exit" "letfn"))
+(define (hc-interop-head? name)
+  (let ((n (string-length name)))
+    (and (> n 1)
+         (or (char=? (string-ref name 0) #\.)
+             (char=? (string-ref name (- n 1)) #\.)))))
+(define (hc-special? name)
+  (if (or (member name hc-special-names) (hc-interop-head? name)) #t #f))
+
+;; --- compile-time environment -----------------------------------------------
+(define (hc-current-ns ctx) (chez-actx-cns ctx))
+(define (hc-late-bind? ctx) #t)            ; Chez has no interpreter to punt to
+
+;; Runtime macros land in inc6b (jolt-r8ku): no macro is emitted as a runtime
+;; value yet, so nothing is a macro. form-macro? is only ever asked about a
+;; non-handled, non-special head (e.g. +, a user fn) — all non-macros today.
+(define (hc-macro? ctx sym) #f)
+(define (hc-expand-1 ctx form)
+  (jolt-throw (jolt-ex-info "form-expand-1: runtime macros not on Chez yet (jolt-r8ku)"
+                            (jolt-hash-map))))
+
+;; Classify a global (non-local) symbol reference against the var registry:
+;;   {:kind :var :ns NS :name NAME}   — a defined var (compile ns / clojure.core)
+;;   {:kind :unresolved :name NAME}   — not found (late-bind -> var-ref @ compile ns;
+;;                                      a qualified one -> host-static in the analyzer)
+;; No :host branch: there is no Janet-style native-op env on Chez — the hot
+;; clojure.core primitives (+,-,map,...) are declared in clojure.core below so
+;; they classify as :var and the emitter's native-op path lowers them.
+(define (hc-resolve-global ctx sym)
+  (let* ((nm (symbol-t-name sym))
+         (sns (symbol-t-ns sym))
+         (qualified (and (not (jolt-nil? sns)) sns))
+         (cell (if qualified
+                   (var-cell-lookup qualified nm)
+                   (or (var-cell-lookup (chez-actx-cns ctx) nm)
+                       (var-cell-lookup "clojure.core" nm)))))
+    (if (and cell (var-cell-defined? cell))
+        (jolt-hash-map hc-kw-kind hc-kw-var
+                       hc-kw-ns (var-cell-ns cell)
+                       hc-kw-name (var-cell-name cell))
+        (jolt-hash-map hc-kw-kind hc-kw-unresolved hc-kw-name nm))))
+
+(define (hc-intern! ctx ns-name nm) (declare-var! ns-name nm) jolt-nil)
+
+;; syntax-quote lowering + record hints land in later increments (6b+); stub so
+;; the contract is complete (not on the macro-free spine).
+(define (hc-syntax-quote-lower ctx inner)
+  (jolt-throw (jolt-ex-info "form-syntax-quote-lower: not on Chez yet (jolt-r8ku)"
+                            (jolt-hash-map))))
+(define (hc-record-type? ctx name) #f)
+(define (hc-record-ctor-key ctx name) jolt-nil)
+(define (hc-record-shapes ctx) (jolt-hash-map))
+(define (hc-inline-enabled? ctx) #f)
+(define (hc-inline-ir ctx ns-name nm) jolt-nil)
+
+;; --- declare the hot clojure.core primitives so resolve-global sees them ------
+;; (mirrors backend_scheme.clj native-ops keys — the emitter lowers these inline,
+;;  so the declared cell's unbound root is never deref'd.)
+(for-each (lambda (nm) (declare-var! "clojure.core" nm))
+  '("+" "-" "*" "/" "<" ">" "<=" ">=" "=" "inc" "dec" "not" "min" "max"
+    "mod" "rem" "quot" "vector" "hash-map" "hash-set" "conj" "get" "nth" "count"
+    "assoc" "dissoc" "contains?" "empty?" "peek" "pop" "first" "rest" "next" "seq"
+    "cons" "list" "reverse" "last" "map" "filter" "remove" "reduce" "into" "concat"
+    "apply" "range" "take" "drop" "keys" "vals" "even?" "odd?" "pos?" "neg?"
+    "zero?" "identity" "ex-info"))
+
+;; --- install: bind the contract into the jolt.host namespace -----------------
+(define (hc-install!)
+  (def-var! "jolt.host" "form-sym?" hc-sym?)
+  (def-var! "jolt.host" "form-sym-name" hc-sym-name)
+  (def-var! "jolt.host" "form-sym-ns" hc-sym-ns)
+  (def-var! "jolt.host" "form-sym-meta" hc-sym-meta)
+  (def-var! "jolt.host" "form-list?" hc-list?)
+  (def-var! "jolt.host" "form-vec?" hc-vec?)
+  (def-var! "jolt.host" "form-map?" hc-map?)
+  (def-var! "jolt.host" "form-set?" hc-set?)
+  (def-var! "jolt.host" "form-char?" hc-char?)
+  (def-var! "jolt.host" "form-literal?" hc-literal?)
+  (def-var! "jolt.host" "form-regex?" hc-regex?)
+  (def-var! "jolt.host" "form-inst?" hc-inst?)
+  (def-var! "jolt.host" "form-uuid?" hc-uuid?)
+  (def-var! "jolt.host" "form-elements" hc-elements)
+  (def-var! "jolt.host" "form-vec-items" hc-vec-items)
+  (def-var! "jolt.host" "form-set-items" hc-set-items)
+  (def-var! "jolt.host" "form-map-pairs" hc-map-pairs)
+  (def-var! "jolt.host" "form-regex-source" hc-regex-source)
+  (def-var! "jolt.host" "form-inst-source" hc-inst-source)
+  (def-var! "jolt.host" "form-uuid-source" hc-uuid-source)
+  (def-var! "jolt.host" "form-position" hc-form-position)
+  (def-var! "jolt.host" "form-special?" hc-special?)
+  (def-var! "jolt.host" "compile-ns" hc-current-ns)
+  (def-var! "jolt.host" "late-bind?" hc-late-bind?)
+  (def-var! "jolt.host" "form-macro?" hc-macro?)
+  (def-var! "jolt.host" "form-expand-1" hc-expand-1)
+  (def-var! "jolt.host" "resolve-global" hc-resolve-global)
+  (def-var! "jolt.host" "host-intern!" hc-intern!)
+  (def-var! "jolt.host" "form-syntax-quote-lower" hc-syntax-quote-lower)
+  (def-var! "jolt.host" "record-type?" hc-record-type?)
+  (def-var! "jolt.host" "record-ctor-key" hc-record-ctor-key)
+  (def-var! "jolt.host" "record-shapes" hc-record-shapes)
+  (def-var! "jolt.host" "inline-enabled?" hc-inline-enabled?)
+  (def-var! "jolt.host" "inline-ir" hc-inline-ir))
+
+(hc-install!)

host/chez/jolt-chez.janet

@@ -11,7 +11,7 @@
 (import ../../src/jolt/api :as api)
 (import ./driver :as d)
 
-(defn- fingerprint []
+(defn fingerprint []
   # Hash the inputs that shape the prelude: the core tiers + the emitter + the
   # Chez RT shims. Any change invalidates the cached prelude.
   (def parts @[])
@@ -32,7 +32,7 @@
     (array/push parts (slurp f)))
   (string/slice (string (hash (string/join parts))) 0))
 
-(defn- ensure-prelude [ctx]
+(defn ensure-prelude [ctx]
   (def dir (or (os/getenv "JOLT_IMAGE_CACHE_DIR") (os/getenv "TMPDIR") "/tmp"))
   (def path (string dir "/jolt-chez-prelude-" (fingerprint) ".ss"))
   (unless (os/stat path)