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Recursive rule calling another rule fails with INT-022 when its second argument is bound #608
Description
Found by the playground/docs audit (2026-10-15): the sports-league tutorial step sl3-s4 errors on v2.0.6 and on v3.
Repro
(transact [[:a :edge :b] [:b :edge :c]])
(rule [(link ?x ?y) [?x :edge ?y]])
(rule [(chain ?x ?y) (link ?x ?y)])
(rule [(chain ?x ?y) (link ?x ?m) (chain ?m ?y)])
(query [:find ?x :where (chain ?x :c)]) ; INT-022 "datalog evaluator: Unbound variable in rule head: ?m"
(query [:find ?y :where (chain :a ?y)]) ; ok: :b :c
(query [:find ?x ?y :where (chain ?x ?y)]) ; ok: 3 rowsThe same chain written with patterns instead of a call to link ([?x :edge ?y] / [?x :edge ?m] (chain ?m ?y)) answers (chain ?x :c) correctly, so the failure is in demand-driven evaluation (magic sets, adornment fb) of a body made of rule calls only. The query is valid and should return ?x = :a, :b.
Same result on main (28f4a4e) and v3 (e078e46). It refuses a query rather than returning wrong rows.
Activity
Merge pull request #609 from project-minigraf/fix/608-magic-sets
adityamukho commentedon Oct 16, 2026
Fixed on
v3by #609 (magic-sets demand now supplied by every call site). Backport to v2.x follows.fix(magic-sets): guard a rule only by demand every call site supplies (…
release: v2.0.7
feat(engine): head constants and constants no cell equals (#551)