Fixed handling of template template default arguments

src/class_diagram/visitor/translation_unit_visitor.cc

@@ -1006,11 +1006,11 @@ bool translation_unit_visitor::process_template_parameters(
                 clang::dyn_cast_or_null<clang::TemplateTemplateParmDecl>(
                     parameter);
             std::optional<std::string> default_arg;
-            if (template_template_parameter->hasDefaultArgument())
+            if (template_template_parameter->hasDefaultArgument()) {
                 default_arg = common::to_string(
                     template_template_parameter->getDefaultArgument()
-                        .getArgument()
+                        .getArgument());
-                        .getAsExpr());
+            }
             auto ct = template_parameter::make_template_template_type(
                 template_template_parameter->getNameAsString(), default_arg,
                 template_template_parameter->isParameterPack());

src/common/clang_utils.cc

@@ -169,6 +169,24 @@ std::string to_string(const clang::RecordType &type,
     return to_string(type.desugar(), ctx, try_canonical);
 }
 
+std::string to_string(const clang::TemplateArgument &arg)
+{
+    switch (arg.getKind()) {
+    case clang::TemplateArgument::Expression:
+        return to_string(arg.getAsExpr());
+    case clang::TemplateArgument::Type:
+        return to_string(arg.getAsType());
+    case clang::TemplateArgument::Null:
+        return "";
+    case clang::TemplateArgument::NullPtr:
+        return "nullptr";
+    case clang::TemplateArgument::Integral:
+        return std::to_string(arg.getAsIntegral().getExtValue());
+    default:
+        return "";
+    }
+}
+
 std::string to_string(const clang::Expr *expr)
 {
     const clang::LangOptions lang_options;

src/common/clang_utils.h

@@ -81,6 +81,8 @@ std::string to_string(const clang::QualType &type, const clang::ASTContext &ctx,
 std::string to_string(const clang::RecordType &type,
     const clang::ASTContext &ctx, bool try_canonical = true);
 
+std::string to_string(const clang::TemplateArgument &arg);
+
 std::string to_string(const clang::Expr *expr);
 
 std::string to_string(const clang::Stmt *stmt);