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Type :long loop-carried vars too (complete round 2)

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loop-kinds only typed :double accumulators; a ^long-seeded loop var (e.g.
(loop [acc start] ...) with a ^long start) stayed generic even though it's sound
to fx-type — :long only ever comes from an explicit hint, and a ^long value is
already coerced to a fixnum at fn entry. Keep the init's kind (:double or :long)
through the fixpoint, demoting only on a recur-arg mismatch.

Integer-literal-init loop vars (a bare (loop [i 0] ...)) still stay generic by
design: :long is never seeded from a literal, so a bignum-producing loop keeps
arbitrary precision.
This commit is contained in:
Yogthos 2026-06-23 17:04:44 -04:00
parent eab18e363c
commit 7d1b9e56d8
3 changed files with 166 additions and 159 deletions
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7
test/chez/numeric-test.ss
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@ -64,6 +64,11 @@
;; precision (no fx* overflow).
(let ((e (emitf "u" "(fn* ([] (loop [acc 1 i 1] (if (< i 25) (recur (* acc i) (inc i)) acc))))")))
(ok "loop integer accumulator is NOT fx-specialized" (not (has? e "(fx*"))))
;; a ^long-seeded loop accumulator IS fx-typed (the hint is a fixnum promise, and
;; the value flows from a coerced ^long param).
(let ((e (emitf "u" "(fn* ([^long start] (loop [acc start] (if (< acc 100) (recur (inc acc)) acc))))")))
(ok "long-seeded loop accumulator lowers (inc acc) to fx1+" (has? e "(fx1+"))
(ok "long-seeded loop comparison lowers to fx<?" (has? e "(fx<?")))
;; --- soundness: un-hinted / integer-literal code stays generic ---
(let ((e (emitf "u" "(fn* ([a b] (+ a b)))")))
@ -92,6 +97,8 @@
(= 15 (jnum->exact (ev "((fn* ([] (loop [acc 0.0 i 0] (if (< i 10) (recur (+ acc 1.5) (inc i)) acc)))))"))))
(ok "loop integer factorial stays exact (bignum preserved)"
(jolt-truthy? (ev "(< 1000000000000000000000 ((fn* ([] (loop [acc 1 i 1] (if (< i 25) (recur (* acc i) (inc i)) acc)))) ))")))
(ok "long-seeded loop accumulator counts to 100"
(= 100 (jnum->exact (ev "((fn* ([^long start] (loop [acc start] (if (< acc 100) (recur (inc acc)) acc)))) 0)"))))
(printf "~a/~a passed~n" (- total fails) total)
(exit (if (zero? fails) 0 1))