bool Sema::ActOnCXXNestedNameSpecifier(Scope *S,
                                       SourceLocation TemplateLoc, 
                                       CXXScopeSpec &SS, 
                                       TemplateTy Template,
                                       SourceLocation TemplateNameLoc,
                                       SourceLocation LAngleLoc,
                                       ASTTemplateArgsPtr TemplateArgsIn,
                                       SourceLocation RAngleLoc,
                                       SourceLocation CCLoc,
                                       bool EnteringContext) {
  if (SS.isInvalid())
    return true;
  
  // Translate the parser's template argument list in our AST format.
  TemplateArgumentListInfo TemplateArgs(LAngleLoc, RAngleLoc);
  translateTemplateArguments(TemplateArgsIn, TemplateArgs);

  if (DependentTemplateName *DTN = Template.get().getAsDependentTemplateName()){
    // Handle a dependent template specialization for which we cannot resolve
    // the template name.
    assert(DTN->getQualifier()
             == static_cast<NestedNameSpecifier*>(SS.getScopeRep()));
    QualType T = Context.getDependentTemplateSpecializationType(ETK_None,
                                                          DTN->getQualifier(),
                                                          DTN->getIdentifier(),
                                                                TemplateArgs);
    
    // Create source-location information for this type.
    TypeLocBuilder Builder;
    DependentTemplateSpecializationTypeLoc SpecTL 
      = Builder.push<DependentTemplateSpecializationTypeLoc>(T);
    SpecTL.setLAngleLoc(LAngleLoc);
    SpecTL.setRAngleLoc(RAngleLoc);
    SpecTL.setKeywordLoc(SourceLocation());
    SpecTL.setNameLoc(TemplateNameLoc);
    SpecTL.setQualifierLoc(SS.getWithLocInContext(Context));
    for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)
      SpecTL.setArgLocInfo(I, TemplateArgs[I].getLocInfo());
    
    SS.Extend(Context, TemplateLoc, Builder.getTypeLocInContext(Context, T), 
              CCLoc);
    return false;
  }
  
  
  if (Template.get().getAsOverloadedTemplate() ||
      isa<FunctionTemplateDecl>(Template.get().getAsTemplateDecl())) {
    SourceRange R(TemplateNameLoc, RAngleLoc);
    if (SS.getRange().isValid())
      R.setBegin(SS.getRange().getBegin());
      
    Diag(CCLoc, diag::err_non_type_template_in_nested_name_specifier)
      << Template.get() << R;
    NoteAllFoundTemplates(Template.get());
    return true;
  }
                                
  // We were able to resolve the template name to an actual template. 
  // Build an appropriate nested-name-specifier.
  QualType T = CheckTemplateIdType(Template.get(), TemplateNameLoc, 
                                   TemplateArgs);
  if (T.isNull())
    return true;

  // Alias template specializations can produce types which are not valid
  // nested name specifiers.
  if (!T->isDependentType() && !T->getAs<TagType>()) {
    Diag(TemplateNameLoc, diag::err_nested_name_spec_non_tag) << T;
    NoteAllFoundTemplates(Template.get());
    return true;
  }

  // Provide source-location information for the template specialization 
  // type.
  TypeLocBuilder Builder;
  TemplateSpecializationTypeLoc SpecTL 
    = Builder.push<TemplateSpecializationTypeLoc>(T);
  
  SpecTL.setLAngleLoc(LAngleLoc);
  SpecTL.setRAngleLoc(RAngleLoc);
  SpecTL.setTemplateNameLoc(TemplateNameLoc);
  for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)
    SpecTL.setArgLocInfo(I, TemplateArgs[I].getLocInfo());


  SS.Extend(Context, TemplateLoc, Builder.getTypeLocInContext(Context, T), 
            CCLoc);
  return false;
}