Add interval internal_hash/equality

Intervals can be added to value sets correctly now we're hashing on
value rather than identity.

Author: jezhiggins

src/analyses/variable-sensitivity/interval_abstract_value.cpp

@@ -282,6 +282,19 @@ exprt interval_abstract_valuet::to_constant() const
 #endif
 }
 
+size_t interval_abstract_valuet::internal_hash() const
+{
+  return std::hash<std::string>{}(interval.pretty());
+}
+
+bool interval_abstract_valuet::internal_equality(
+  const abstract_object_pointert &other) const
+{
+  auto cast_other =
+    std::dynamic_pointer_cast<const interval_abstract_valuet>(other);
+  return cast_other && interval == cast_other->interval;
+}
+
 void interval_abstract_valuet::output(
   std::ostream &out,
   const ai_baset &ai,

src/analyses/variable-sensitivity/interval_abstract_value.h

@@ -46,6 +46,9 @@ class interval_abstract_valuet : public abstract_value_objectt
     return interval;
   }
 
+  size_t internal_hash() const override;
+  bool internal_equality(const abstract_object_pointert &other) const override;
+
   void output(
     std::ostream &out,
     const class ai_baset &ai,

unit/analyses/variable-sensitivity/value_expression_evaluation/expression_evaluation.cpp

@@ -595,9 +595,9 @@ SCENARIO(
       auto op2 = make_value_set({interval12, val1}, environment, ns);
       auto result = add_as_value_set(op1, op2, environment, ns);
 
-      THEN("= { [2,4], [2,3], [2,3], 2 }")
-      { // duplicate interval ok as first pass. Will be eliminated in due course.
-        EXPECT(result, {interval24, interval23, interval23, val2});
+      THEN("= { [2,4], [2,3], 2 }")
+      {
+        EXPECT(result, {interval24, interval23, val2});
       }
     }
   }