Remove subtyping for sets theory (#5179)

This PR removes subtyping for sets theory due to issues like #4502, #4507 and #4631.
Changes:

Add SingletonOp for singletons to specify the type of the single element in the set.
Add mkSingleton to the solver to enable the user to pass the sort of the single element.
Update smt and cvc parsers to use mkSingleton when the kind is SINGLETON

1 files changed, 11 insertions, 0 deletions

diff --git a/src/expr/node_manager.cpp b/src/expr/node_manager.cpp
index 3c3d6df4a..f8057006c 100644
--- a/src/expr/node_manager.cpp
+++ b/src/expr/node_manager.cpp
@@ -950,6 +950,17 @@ Node NodeManager::mkNullaryOperator(const TypeNode& type, Kind k) {
   }
 }
 
+Node NodeManager::mkSingleton(const TypeNode& t, const TNode n)
+{
+  Assert(n.getType().isSubtypeOf(t))
+      << "Invalid operands for mkSingleton. The type '" << n.getType()
+      << "' of node '" << n << "' is not a subtype of '" << t << "'."
+      << std::endl;
+  Node op = mkConst(SingletonOp(t));
+  Node singleton = mkNode(kind::SINGLETON, op, n);
+  return singleton;
+}
+
 Node NodeManager::mkAbstractValue(const TypeNode& type) {
   Node n = mkConst(AbstractValue(++d_abstractValueCount));
   n.setAttribute(TypeAttr(), type);