[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.

4 files changed, 17 insertions, 8 deletions

diff --git a/clang-tools-extra/clang-tidy/bugprone/ForwardingReferenceOverloadCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ForwardingReferenceOverloadCheck.cpp
index 36687a8..c87b3ea 100644
--- a/clang-tools-extra/clang-tidy/bugprone/ForwardingReferenceOverloadCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/ForwardingReferenceOverloadCheck.cpp
@@ -54,7 +54,9 @@ AST_MATCHER(QualType, isEnableIf) {
 AST_MATCHER_P(TemplateTypeParmDecl, hasDefaultArgument,
               clang::ast_matchers::internal::Matcher<QualType>, TypeMatcher) {
   return Node.hasDefaultArgument() &&
-         TypeMatcher.matches(Node.getDefaultArgument(), Finder, Builder);
+         TypeMatcher.matches(
+             Node.getDefaultArgument().getArgument().getAsType(), Finder,
+             Builder);
 }
 AST_MATCHER(TemplateDecl, hasAssociatedConstraints) {
   return Node.hasAssociatedConstraints();
diff --git a/clang-tools-extra/clang-tidy/bugprone/IncorrectEnableIfCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/IncorrectEnableIfCheck.cpp
index 09aaf3e..75f1107 100644
--- a/clang-tools-extra/clang-tidy/bugprone/IncorrectEnableIfCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/IncorrectEnableIfCheck.cpp
@@ -19,10 +19,11 @@ namespace {
 AST_MATCHER_P(TemplateTypeParmDecl, hasUnnamedDefaultArgument,
               ast_matchers::internal::Matcher<TypeLoc>, InnerMatcher) {
   if (Node.getIdentifier() != nullptr || !Node.hasDefaultArgument() ||
-      Node.getDefaultArgumentInfo() == nullptr)
+      Node.getDefaultArgument().getArgument().isNull())
     return false;
 
-  TypeLoc DefaultArgTypeLoc = Node.getDefaultArgumentInfo()->getTypeLoc();
+  TypeLoc DefaultArgTypeLoc =
+      Node.getDefaultArgument().getTypeSourceInfo()->getTypeLoc();
   return InnerMatcher.matches(DefaultArgTypeLoc, Finder, Builder);
 }
 
diff --git a/clang-tools-extra/clang-tidy/modernize/UseConstraintsCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseConstraintsCheck.cpp
index 7a021fe..ea4d995 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseConstraintsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseConstraintsCheck.cpp
@@ -177,9 +177,11 @@ matchTrailingTemplateParam(const FunctionTemplateDecl *FunctionTemplate) {
           dyn_cast<TemplateTypeParmDecl>(LastParam)) {
     if (LastTemplateParam->hasDefaultArgument() &&
         LastTemplateParam->getIdentifier() == nullptr) {
-      return {matchEnableIfSpecialization(
-                  LastTemplateParam->getDefaultArgumentInfo()->getTypeLoc()),
-              LastTemplateParam};
+      return {
+          matchEnableIfSpecialization(LastTemplateParam->getDefaultArgument()
+                                          .getTypeSourceInfo()
+                                          ->getTypeLoc()),
+          LastTemplateParam};
     }
   }
   return {};
diff --git a/clang-tools-extra/clangd/Hover.cpp b/clang-tools-extra/clangd/Hover.cpp
index 06b949b..2ec0994 100644
--- a/clang-tools-extra/clangd/Hover.cpp
+++ b/clang-tools-extra/clangd/Hover.cpp
@@ -247,8 +247,12 @@ fetchTemplateParameters(const TemplateParameterList *Params,
       if (!TTP->getName().empty())
         P.Name = TTP->getNameAsString();
 
-      if (TTP->hasDefaultArgument())
-        P.Default = TTP->getDefaultArgument().getAsString(PP);
+      if (TTP->hasDefaultArgument()) {
+        P.Default.emplace();
+        llvm::raw_string_ostream Out(*P.Default);
+        TTP->getDefaultArgument().getArgument().print(PP, Out,
+                                                      /*IncludeType=*/false);
+      }
     } else if (const auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
       P.Type = printType(NTTP, PP);