[clang] NFCI: use TemplateArgumentLoc for type-param DefaultArgument (#92854)

This is an enabler for a future patch.

This allows an type-parameter default argument to be set as an arbitrary
TemplateArgument, not just a type.
This allows template parameter packs to have default arguments in the
AST, even though the language proper doesn't support the syntax for it.

This will be used in a later patch which synthesizes template parameter
lists with arbitrary default arguments taken from template
specializations.

There are a few places we used SubsType, because we only had a type, now
we use SubstTemplateArgument.
SubstTemplateArgument was missing arguments for setting Instantiation
location and entity names.
Adding those is needed so we don't regress in diagnostics.

1 files changed, 4 insertions, 4 deletions

diff --git a/clang/lib/ExtractAPI/DeclarationFragments.cpp b/clang/lib/ExtractAPI/DeclarationFragments.cpp
index 98b9343..d88e4e0 100644
--- a/clang/lib/ExtractAPI/DeclarationFragments.cpp
+++ b/clang/lib/ExtractAPI/DeclarationFragments.cpp
@@ -999,11 +999,11 @@ DeclarationFragmentsBuilder::getFragmentsForTemplateParameters(
             DeclarationFragments::FragmentKind::GenericParameter);
 
       if (TemplateParam->hasDefaultArgument()) {
-        DeclarationFragments After;
+        const auto Default = TemplateParam->getDefaultArgument();
         Fragments.append(" = ", DeclarationFragments::FragmentKind::Text)
-            .append(getFragmentsForType(TemplateParam->getDefaultArgument(),
-                                        TemplateParam->getASTContext(), After));
-        Fragments.append(std::move(After));
+            .append(getFragmentsForTemplateArguments(
+                {Default.getArgument()}, TemplateParam->getASTContext(),
+                {Default}));
       }
     } else if (const auto *NTP =
                    dyn_cast<NonTypeTemplateParmDecl>(ParameterArray[i])) {