[clang] [Clang] [Sema] Added a check for `NameInfo` actually containing a valid destructor name (PR #210610)

[Soham Karandikar via cfe-commits]

https://github.com/skadewdl3 created https://github.com/llvm/llvm-project/pull/210610

Fixes #210234 

As per my investigation (mostly following stack traces and dumping variable values), a default empty `DeclarationNameInfo` was being returned after template substitution [over here](https://github.com/llvm/llvm-project/blob/c45b4e4d00bed488d6ece5608560561732ae5b9e/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp#L3270).

```cpp
// D-.>getNameInfo() has actual data here
 
 DeclarationNameInfo NameInfo
    = SemaRef.SubstDeclarationNameInfo(D->getNameInfo(), TemplateArgs);

// NameInfo has default values
```

This was being passed on directly to `CXXDestructorDecl::Create` leading to the assertion being hit. This PR adds a check that ensures `NameInfo` actually contains a valid destructor name before constructing a `CXXDestructorDecl`. This fixes the assertion being hit in the reproducer from the linked issue.

>From 28cd7775fba49e938db8f79d1ce8c55adbeebccb Mon Sep 17 00:00:00 2001
From: Soham Karandikar <sohamk10 at gmail.com>
Date: Sun, 19 Jul 2026 21:55:54 +0530
Subject: [PATCH] Added a check for `NameInfo` actually containing a valid
 destructor name

---
 clang/lib/Sema/SemaTemplateInstantiateDecl.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index c2e90624b8a6e..30ddad02f63c2 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -3287,7 +3287,10 @@ Decl *TemplateDeclInstantiator::VisitCXXMethodDecl(
         TrailingRequiresClause);
     Method->setRangeEnd(Constructor->getEndLoc());
   } else if (CXXDestructorDecl *Destructor = dyn_cast<CXXDestructorDecl>(D)) {
-    Method = CXXDestructorDecl::Create(
+      if (NameInfo.getName().getNameKind() != DeclarationName::NameKind::CXXDestructorName) {
+          return nullptr;
+      }
+      Method = CXXDestructorDecl::Create(
         SemaRef.Context, Record, StartLoc, NameInfo, T, TInfo,
         Destructor->UsesFPIntrin(), Destructor->isInlineSpecified(), false,
         Destructor->getConstexprKind(), TrailingRequiresClause);