C++: introduce template_parameter_symbol_type

The C++ front-end uses symbol_typet to represent template parameter types.
It also uses the same irep to represent typedefs and struct/union tags.

This commit disambiguates the meaning of this irep by introducing a separate
type, called template_parameter_symbol_type.

Author: Daniel Kroening

src/cpp/cpp_template_parameter.h

@@ -62,11 +62,11 @@ struct template_parametert:public exprt
 };
 
 /// a template parameter symbol that is a type
-struct template_parameter_symbol_typet:public typet
+struct template_parameter_symbol_typet : public typet
 {
 public:
-  explicit template_parameter_symbol_typet(
-    const irep_idt &identifier):typet(ID_template_parameter_symbol_type)
+  explicit template_parameter_symbol_typet(const irep_idt &identifier)
+    : typet(ID_template_parameter_symbol_type)
   {
     set_identifier(identifier);
   }
@@ -90,16 +90,18 @@ struct template_parameter_symbol_typet:public typet
 ///
 /// \param type: Source type.
 /// \return Object of type \ref template_parameter_symbol_typet.
-inline const template_parameter_symbol_typet &to_template_parameter_symbol_type(const typet &type)
+inline const template_parameter_symbol_typet &
+to_template_parameter_symbol_type(const typet &type)
 {
-  PRECONDITION(type.id()==ID_template_parameter_symbol_type);
+  PRECONDITION(type.id() == ID_template_parameter_symbol_type);
   return static_cast<const template_parameter_symbol_typet &>(type);
 }
 
 /// \copydoc to_template_parameter_symbol_type(const typet &)
-inline template_parameter_symbol_typet &to_template_parameter_symbol_type(typet &type)
+inline template_parameter_symbol_typet &
+to_template_parameter_symbol_type(typet &type)
 {
-  PRECONDITION(type.id()==ID_template_parameter_symbol_type);
+  PRECONDITION(type.id() == ID_template_parameter_symbol_type);
   return static_cast<template_parameter_symbol_typet &>(type);
 }
 

src/cpp/cpp_typecheck_resolve.cpp

@@ -2271,9 +2271,9 @@ void cpp_typecheck_resolvet::filter_for_named_scopes(
       if(e.id()!=ID_type)
         continue; // expressions are definitively not a scope
 
-      if(e.type().id() == ID_symbol_type)
+      if(e.type().id() == ID_template_parameter_symbol_type)
       {
-        symbol_typet type=to_symbol_type(e.type());
+        auto type = to_template_parameter_symbol_type(e.type());
 
         while(true)
         {
@@ -2282,8 +2282,8 @@ void cpp_typecheck_resolvet::filter_for_named_scopes(
           const symbolt &symbol=cpp_typecheck.lookup(identifier);
           assert(symbol.is_type);
 
-          if(symbol.type.id() == ID_symbol_type)
-            type=to_symbol_type(symbol.type);
+          if(symbol.type.id() == ID_template_parameter_symbol_type)
+            type = to_template_parameter_symbol_type(symbol.type);
           else if(symbol.type.id()==ID_struct ||
                   symbol.type.id()==ID_union ||
                   symbol.type.id()==ID_c_enum)