LOGIC-82: lcons with nil tail fails to unify properly

clojure · Dec 21, 2012 · 0c985df · 0c985df
1 parent cb91306
commit 0c985df
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Showing 2 changed files with 11 additions and 1 deletion.
diff --git a/src/main/clojure/clojure/core/logic.clj b/src/main/clojure/clojure/core/logic.clj
@@ -1514,7 +1514,9 @@
             nil)
           (unify s u v))
         (if (lvar? u)
-          (unify s u '())
+          (if-let [s (unify s u '())]
+            s
+            (unify s u nil))
           nil)))))
 
 ;; -----------------------------------------------------------------------------

diff --git a/src/test/clojure/clojure/core/logic/tests.clj b/src/test/clojure/clojure/core/logic/tests.clj
@@ -1286,6 +1286,14 @@
                (== q (lcons x y)))))
          (into #{} [(lcons 1 '_0) (lcons 2 '_0) (lcons 3 '_0)]))))
 
+(deftest test-82-nil-lcons-tail
+  (is (= (run 1 [q]
+           (fresh [a b c]
+             (conso a b c)
+             (== b nil)
+             (== `(~a) c)))
+         '(_0))))
+
 ;; =============================================================================
 ;; cKanren