datalog: mixed-EDB+IDB-same-relation regression test (220/220)

lib/datalog/tests/eval.sx

@@ -273,6 +273,17 @@
           (dl-saturated? db))
         false)
 
+      ;; A relation can be both EDB-seeded and rule-derived;
+      ;; saturate combines facts + derivations.
+      (dl-et-test-set! "mixed EDB + IDB same relation"
+        (dl-query
+          (dl-program
+            "link(a, b). link(c, d). link(e, c).
+             via(a, e).
+             link(X, Y) :- via(X, M), link(M, Y).")
+          (list (quote link) (quote a) (quote X)))
+        (list {:X (quote b)} {:X (quote c)}))
+
       (dl-et-test! "saturated? after assert"
         (let ((db (dl-program
                     "parent(a, b).