Set declared_on_type for precise EVSs

This is in entryt, and its close relative fieldnamet. We now make sure
it is well-defined by always setting it to one special value.

Author: Owen Jones

src/pointer-analysis/external_value_set_expr.h

@@ -294,6 +294,12 @@ class external_value_set_exprt:public exprt
       return copy;
     }
   }
+
+  static const typet &get_precise_evs_irep_id()
+  {
+    static typet precise_evs("precise_evs");
+    return precise_evs;
+  }
 };
 
 inline external_value_set_exprt &to_external_value_set(exprt &e)

src/pointer-analysis/local_value_set.cpp

@@ -45,12 +45,13 @@ local_value_sett::init_per_field_external_value_set(
   const external_value_set_exprt &evse)
 {
   PRECONDITION(!evse.access_path_entries().empty());
-  const auto &apback=evse.access_path_entries().back();
-  std::string basename=evse.get_access_path_basename(apback.declared_on_type());
+  const typet &declared_on_type =
+    evse.access_path_entries().back().declared_on_type();
+  std::string basename = evse.get_access_path_basename(declared_on_type);
   std::string access_path_suffix=evse.get_access_path_suffix();
   std::string entryname=basename+access_path_suffix;
 
-  entryt entry(basename, access_path_suffix, apback.declared_on_type(), evse);
+  entryt entry(basename, access_path_suffix, declared_on_type, evse);
 
   auto insert_result=values.insert(std::make_pair(irep_idt(entryname), entry));
 
@@ -65,9 +66,9 @@ void local_value_sett::init_precise_external_value_set(
   object_mapt &dest)
 {
   PRECONDITION(!evse.access_path_entries().empty());
-  const auto &apback = evse.access_path_entries().back();
-  std::string basename =
-    evse.get_access_path_basename(apback.declared_on_type());
+  const typet &declared_on_type =
+    external_value_set_exprt::get_precise_evs_irep_id();
+  std::string basename = evse.get_access_path_basename(declared_on_type);
   std::string access_path_suffix = evse.get_access_path_suffix();
   std::string entryname = basename + access_path_suffix;
 
@@ -624,7 +625,10 @@ void local_value_sett::assign_rec(
         std::string entryname=basename+access_path_suffix;
 
         entryt entry(
-          basename, access_path_suffix, declared_on_type, new_ext_set);
+          basename,
+          access_path_suffix,
+          external_value_set_exprt::get_precise_evs_irep_id(),
+          new_ext_set);
 
         auto insert_result=const_cast<valuest &>(values).
           insert(std::make_pair(irep_idt(entryname), entry));