Move is_class and default_access to struct_typet

A class_typet would always return true for is_class() and ID_private for
default_access(). Only when available for both a struct_typet and a
class_typet do they enable non-trivial use.

Author: tautschnig

src/cpp/cpp_typecheck_bases.cpp

@@ -18,8 +18,7 @@ void cpp_typecheckt::typecheck_compound_bases(struct_typet &type)
   std::set<irep_idt> bases;
   std::set<irep_idt> vbases;
 
-  irep_idt default_class_access=
-    type.get_bool(ID_C_class)?ID_private:ID_public;
+  irep_idt default_class_access = type.default_access();
 
   irept::subt &bases_irep=type.add(ID_bases).get_sub();
 

src/cpp/cpp_typecheck_compound_type.cpp

@@ -977,8 +977,7 @@ void cpp_typecheckt::typecheck_compound_body(symbolt &symbol)
   symbol.type.set(ID_name, symbol.name);
 
   // default access
-  irep_idt access=
-    type.get_bool(ID_C_class)?ID_private:ID_public;
+  irep_idt access = type.default_access();
 
   bool found_ctor=false;
   bool found_dtor=false;
@@ -1119,8 +1118,7 @@ void cpp_typecheckt::typecheck_compound_body(symbolt &symbol)
   }
 
   // Reset the access type
-  access=
-    type.get_bool(ID_C_class)?ID_private:ID_public;
+  access = type.default_access();
 
   // All the data members are now known.
   // We now deal with the constructors that we are given.

src/util/std_types.h

@@ -216,6 +216,19 @@ class struct_union_typet:public typet
 
   irep_idt get_tag() const { return get(ID_tag); }
   void set_tag(const irep_idt &tag) { set(ID_tag, tag); }
+
+  /// A struct may be a class, where members may have access restrictions.
+  bool is_class() const
+  {
+    return id() == ID_struct && get_bool(ID_C_class);
+  }
+
+  /// Return the access specification for members where access has not been
+  /// modified.
+  irep_idt default_access() const
+  {
+    return is_class() ? ID_private : ID_public;
+  }
 };
 
 /// Check whether a reference to a typet is a \ref struct_union_typet.
@@ -313,16 +326,6 @@ class class_typet:public struct_typet
     return (methodst &)(add(ID_methods).get_sub());
   }
 
-  bool is_class() const
-  {
-    return get_bool(ID_C_class);
-  }
-
-  irep_idt default_access() const
-  {
-    return is_class()?ID_private:ID_public;
-  }
-
   class baset:public exprt
   {
   public: