Use ns.follow on type of struct

Implementation moved into `.cpp` as it was getting bigger and required
the full include of `namespace.h`, not just a forward declaration.

Author: thomasspriggs

src/util/std_expr.cpp

@@ -8,6 +8,8 @@ Author: Daniel Kroening, [email protected]
 
 #include "std_expr.h"
 
+#include <util/namespace.h>
+
 #include <cassert>
 
 #include "arith_tools.h"
@@ -167,3 +169,22 @@ address_of_exprt::address_of_exprt(const exprt &_op):
   unary_exprt(ID_address_of, _op, pointer_type(_op.type()))
 {
 }
+
+/// \return The expression for a named component of this struct.
+exprt &struct_exprt::component(const irep_idt &name, const namespacet &ns)
+{
+  const auto index = to_struct_type(ns.follow(type())).component_number(name);
+  DATA_INVARIANT(
+    index < operands().size(), "component matching index should exist");
+  return operands()[index];
+}
+
+/// \return The expression for a named component of this struct.
+const exprt &
+struct_exprt::component(const irep_idt &name, const namespacet &ns) const
+{
+  const auto index = to_struct_type(ns.follow(type())).component_number(name);
+  DATA_INVARIANT(
+    index < operands().size(), "component matching index should exist");
+  return operands()[index];
+}

src/util/std_expr.h

@@ -1824,23 +1824,8 @@ class struct_exprt:public exprt
   {
   }
 
-  /// \return The expression for a named component of this struct.
-  exprt &component(const irep_idt &name)
-  {
-    const auto index = to_struct_type(type()).component_number(name);
-    DATA_INVARIANT(
-      index < operands().size(), "component matching index should exist");
-    return operands()[index];
-  }
-
-  /// \return The expression for a named component of this struct.
-  const exprt &component(const irep_idt &name) const
-  {
-    const auto index = to_struct_type(type()).component_number(name);
-    DATA_INVARIANT(
-      index < operands().size(), "component matching index should exist");
-    return operands()[index];
-  }
+  exprt &component(const irep_idt &name, const namespacet &ns);
+  const exprt &component(const irep_idt &name, const namespacet &ns) const;
 };
 
 /*! \brief Cast a generic exprt to a \ref struct_exprt