[quantifiers] Fix prenex computation (#5879)

Previously our prenex computation could generate quantifiers of the form forall x y y. F, which would lead to an assertion failure in getFreeVariablesScope, as it assumes that no shadowing occurs. This commit makes the prenex computation take a set rather than a vector, thus avoiding duplications of prenexed variables. It also changes mkForall to take a constant vector, since it does not modify the given vector.

Fixes #5693 

3 files changed, 28 insertions, 0 deletions

diff --git a/test/regress/CMakeLists.txt b/test/regress/CMakeLists.txt
index ddf810b0c..1e4f42ffd 100644
--- a/test/regress/CMakeLists.txt
+++ b/test/regress/CMakeLists.txt
@@ -847,6 +847,7 @@ set(regress_0_tests
   regress0/quantifiers/issue4437-unc-quant.smt2
   regress0/quantifiers/issue4576.smt2
   regress0/quantifiers/issue5645-dt-cm-spurious.smt2
+  regress0/quantifiers/issue5693-prenex.smt2
   regress0/quantifiers/lra-triv-gn.smt2
   regress0/quantifiers/macros-int-real.smt2
   regress0/quantifiers/macros-real-arg.smt2
@@ -1784,6 +1785,7 @@ set(regress_1_tests
   regress1/quantifiers/nra-interleave-inst.smt2
   regress1/quantifiers/opisavailable-12.smt2
   regress1/quantifiers/parametric-lists.smt2
+  regress1/quantifiers/prenex-scholl-smt08_RNDPRE_RNDPRE_4_6.smt2
   regress1/quantifiers/psyco-001-bv.smt2
   regress1/quantifiers/psyco-107-bv.smt2
   regress1/quantifiers/psyco-196.smt2
diff --git a/test/regress/regress0/quantifiers/issue5693-prenex.smt2 b/test/regress/regress0/quantifiers/issue5693-prenex.smt2
new file mode 100644
index 000000000..15ee0e7cf
--- /dev/null
+++ b/test/regress/regress0/quantifiers/issue5693-prenex.smt2
@@ -0,0 +1,7 @@
+; COMMAND-LINE: --full-saturate-quant -i --no-check-unsat-cores
+; EXPECT: unsat
+(set-logic ALL)
+(set-option :pre-skolem-quant true)
+(declare-fun v7 () Bool)
+(assert (forall ((q49 Bool) (q55 Bool)) (xor v7 (exists ((q49 Bool)) (xor v7 q49 q49)) v7 (= q55 q49))))
+(check-sat)
\ No newline at end of file
diff --git a/test/regress/regress1/quantifiers/prenex-scholl-smt08_RNDPRE_RNDPRE_4_6.smt2 b/test/regress/regress1/quantifiers/prenex-scholl-smt08_RNDPRE_RNDPRE_4_6.smt2
new file mode 100644
index 000000000..f0a4560d1
--- /dev/null
+++ b/test/regress/regress1/quantifiers/prenex-scholl-smt08_RNDPRE_RNDPRE_4_6.smt2
@@ -0,0 +1,19 @@
+(set-info :smt-lib-version 2.6)
+(set-logic LRA)
+(set-info :source |
+   Scholl, Christoph; Disch, Stefan; Pigorsch, Florian and Kupferschmid,
+   Stefan; Using an SMT Solver and Craig Interpolation to Detect and Remove
+   Redundant Linear Constraints in Representations of Non-Convex Polyhedra.
+   Proceedings of 6th International Workshop on Satisfiability Modulo
+   Theories, Princeton, USA, July 2008.
+   <http://abs.informatik.uni-freiburg.de/smtbench/>
+|)
+(set-info :category "random")
+(set-info :status unsat)
+(declare-fun x1 () Real)
+(declare-fun x2 () Real)
+(declare-fun x3 () Real)
+(declare-fun x4 () Real)
+(assert (forall ((?x1 Real)) (exists ((?x2 Real)) (forall ((?x3 Real)) (exists ((?x4 Real)) (or (and (and (and (>= (+ (+ (* (- 54) ?x1) (* 62 ?x3)) (* (- 53) ?x4)) 79) (not (= (+ (+ (* (- 49) ?x1) (* 25 ?x2)) (* 51 ?x3)) 12))) (or (< (+ (+ (* 5 ?x1) (* 20 ?x2)) (* (- 1) ?x3)) 0) (not (= (+ (+ (* 58 ?x1) (* 61 ?x2)) (* 74 ?x3)) (- 18))))) (or (and (>= (+ (+ (* 48 ?x1) (* (- 47) ?x2)) (* 1 ?x4)) 61) (>= (+ (+ (* (- 19) ?x1) (* (- 80) ?x2)) (* (- 66) ?x3)) 25)) (and (<= (+ (+ (* (- 63) ?x2) (* (- 98) ?x3)) (* (- 4) ?x4)) (- 28)) (not (= (+ (+ (+ (* 10 ?x1) (* 47 ?x2)) (* 77 ?x3)) (* 73 ?x4)) 72))))) (and (or (or (= (+ (+ (* 40 ?x1) (* 16 ?x3)) (* 33 ?x4)) 0) (not (= (+ (+ (* 94 ?x2) (* (- 32) ?x3)) (* (- 19) ?x4)) (- 6)))) (or (not (= (+ (+ (+ (* (- 8) ?x1) (* (- 45) ?x2)) (* 34 ?x3)) (* 11 ?x4)) 57)) (> (+ (* (- 7) ?x2) (* (- 17) ?x3)) 0))) (and (< (+ (+ (+ (* 51 ?x1) (* 5 ?x2)) (* (- 86) ?x3)) (* (- 33) ?x4)) (- 32)) (and (>= (+ (* 50 ?x1) (* (- 46) ?x4)) 37) (not (= (+ (* (- 95) ?x2) (* (- 96) ?x4)) (- 24))))))))))))
+(check-sat)
+(exit)