Implement TypeNode::isComparableTo() and add a unit test for it.

2 files changed, 19 insertions, 0 deletions

diff --git a/src/expr/type_node.cpp b/src/expr/type_node.cpp
index 8cfb6387a..4ddb01974 100644
--- a/src/expr/type_node.cpp
+++ b/src/expr/type_node.cpp
@@ -102,6 +102,19 @@ bool TypeNode::isSubtypeOf(TypeNode t) const {
   return false;
 }
 
+bool TypeNode::isComparableTo(TypeNode t) const {
+  if(*this == t) {
+    return true;
+  }
+  if(isSubtypeOf(NodeManager::currentNM()->realType())) {
+    return t.isSubtypeOf(NodeManager::currentNM()->realType());
+  }
+  if(isPredicateSubtype()) {
+    return t.isComparableTo(getSubtypeBaseType());
+  }
+  return false;
+}
+
 Node TypeNode::getSubtypePredicate() const {
   Assert(isPredicateSubtype());
   return Node::fromExpr(getConst<Predicate>());
diff --git a/src/expr/type_node.h b/src/expr/type_node.h
index f59ce2dfe..7fe3bc75e 100644
--- a/src/expr/type_node.h
+++ b/src/expr/type_node.h
@@ -450,6 +450,12 @@ public:
   /** Is this type a subtype of the given type? */
   bool isSubtypeOf(TypeNode t) const;
 
+  /**
+   * Is this type comparable to the given type (i.e., do they share
+   * a common ancestor in the subtype tree)?
+   */
+  bool isComparableTo(TypeNode t) const;
+
   /** Is this the Boolean type? */
   bool isBoolean() const;