[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 updated https://github.com/llvm/llvm-project/pull/210610

>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 1/3] 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);

>From 7bb6ae3f23d571d3a20e9966568c6890ed0f0563 Mon Sep 17 00:00:00 2001
From: Soham Karandikar <sohamk10 at gmail.com>
Date: Mon, 20 Jul 2026 00:48:41 +0530
Subject: [PATCH 2/3] Simplified if-statement, ran clang-format

---
 clang/lib/Sema/SemaTemplateInstantiateDecl.cpp | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 30ddad02f63c2..df559711f1674 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -3287,10 +3287,11 @@ Decl *TemplateDeclInstantiator::VisitCXXMethodDecl(
         TrailingRequiresClause);
     Method->setRangeEnd(Constructor->getEndLoc());
   } else if (CXXDestructorDecl *Destructor = dyn_cast<CXXDestructorDecl>(D)) {
-      if (NameInfo.getName().getNameKind() != DeclarationName::NameKind::CXXDestructorName) {
-          return nullptr;
-      }
-      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);

>From b532607410ae8af37e8f7c5c99aeb62b05c432d3 Mon Sep 17 00:00:00 2001
From: Soham Karandikar <sohamk10 at gmail.com>
Date: Thu, 23 Jul 2026 00:05:12 -0500
Subject: [PATCH 3/3] Moved empty `DeclarationNameInfo` check after template
 instantiaion, added lit test

---
 clang/lib/Sema/SemaTemplateInstantiateDecl.cpp |  9 +++++----
 clang/test/SemaTemplate/friend.cpp             | 13 +++++++++++++
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index df559711f1674..cff4f17d35bfc 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -3271,6 +3271,11 @@ Decl *TemplateDeclInstantiator::VisitCXXMethodDecl(
   DeclarationNameInfo NameInfo
     = SemaRef.SubstDeclarationNameInfo(D->getNameInfo(), TemplateArgs);
 
+  // Check if the substitution of template args failed
+  // leading to an empty DeclarationNameInfo.
+  if (!NameInfo.getName())
+    return nullptr;
+
   if (FunctionRewriteKind != RewriteKind::None)
     adjustForRewrite(FunctionRewriteKind, D, T, TInfo, NameInfo);
 
@@ -3287,10 +3292,6 @@ Decl *TemplateDeclInstantiator::VisitCXXMethodDecl(
         TrailingRequiresClause);
     Method->setRangeEnd(Constructor->getEndLoc());
   } else if (CXXDestructorDecl *Destructor = dyn_cast<CXXDestructorDecl>(D)) {
-    if (NameInfo.getName().getNameKind() !=
-        DeclarationName::NameKind::CXXDestructorName)
-      return nullptr;
-
     Method = CXXDestructorDecl::Create(
         SemaRef.Context, Record, StartLoc, NameInfo, T, TInfo,
         Destructor->UsesFPIntrin(), Destructor->isInlineSpecified(), false,
diff --git a/clang/test/SemaTemplate/friend.cpp b/clang/test/SemaTemplate/friend.cpp
index aef2faced6a96..6aca7ad90a127 100644
--- a/clang/test/SemaTemplate/friend.cpp
+++ b/clang/test/SemaTemplate/friend.cpp
@@ -180,3 +180,16 @@ namespace InstQualifier1 {
     };
   }
 } // namespace InstQualifier1
+
+namespace invalid_function_name_in_template_instantiation {
+  template <typename T>
+  struct D {
+    friend T::S::~ffl_fusion(); // expected-error {{no type named 'ffl_fusion'}}
+  };
+
+  struct Q {
+    struct S { ~S(); };
+  };
+
+  template struct D<Q>; // expected-note {{in instantiation of template class}}
+} // namespace invalid_function_name_in_template_instantiation