[clang] [clang] Make nullability-on-classes more robust to redeclarations (PR #114778)

[Sam McCall via cfe-commits]

https://github.com/sam-mccall updated https://github.com/llvm/llvm-project/pull/114778

>From 58baaccd4849fee2f8f1966de62660cb4c5bfa6d Mon Sep 17 00:00:00 2001
From: Sam McCall <sam.mccall at gmail.com>
Date: Mon, 4 Nov 2024 12:48:35 +0100
Subject: [PATCH 1/2] [clang] Make nullability-on-classes more robust to
 redeclarations

This is relevant after b24650e814e55d90acfc40acf045456c98f32b9c where
the selected template decl can be anything, even apparently a friend
declaration in some cases.
---
 clang/lib/AST/Type.cpp                    | 18 ++++++++++-----
 clang/test/SemaCXX/nullability_redecl.cpp | 27 +++++++++++++++++++++++
 2 files changed, 40 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/nullability_redecl.cpp

diff --git a/clang/lib/AST/Type.cpp b/clang/lib/AST/Type.cpp
index 229721aeae8114..a01d7be0cacc95 100644
--- a/clang/lib/AST/Type.cpp
+++ b/clang/lib/AST/Type.cpp
@@ -44,6 +44,7 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/FoldingSet.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"
@@ -4774,7 +4775,10 @@ bool Type::canHaveNullability(bool ResultIfUnknown) const {
                 ->getTemplateName()
                 .getAsTemplateDecl())
       if (auto *CTD = dyn_cast<ClassTemplateDecl>(templateDecl))
-        return CTD->getTemplatedDecl()->hasAttr<TypeNullableAttr>();
+        return llvm::any_of(
+            CTD->redecls(), [](const RedeclarableTemplateDecl *RTD) {
+              return RTD->getTemplatedDecl()->hasAttr<TypeNullableAttr>();
+            });
     return ResultIfUnknown;
 
   case Type::Builtin:
@@ -4841,10 +4845,14 @@ bool Type::canHaveNullability(bool ResultIfUnknown) const {
     // For template specializations, look only at primary template attributes.
     // This is a consistent regardless of whether the instantiation is known.
     if (const auto *CTSD = dyn_cast<ClassTemplateSpecializationDecl>(RD))
-      return CTSD->getSpecializedTemplate()
-          ->getTemplatedDecl()
-          ->hasAttr<TypeNullableAttr>();
-    return RD->hasAttr<TypeNullableAttr>();
+      return llvm::any_of(
+          CTSD->getSpecializedTemplate()->redecls(),
+          [](const RedeclarableTemplateDecl *RTD) {
+            return RTD->getTemplatedDecl()->hasAttr<TypeNullableAttr>();
+          });
+    return llvm::any_of(RD->redecls(), [](const TagDecl *RD) {
+      return RD->hasAttr<TypeNullableAttr>();
+    });
   }
 
   // Non-pointer types.
diff --git a/clang/test/SemaCXX/nullability_redecl.cpp b/clang/test/SemaCXX/nullability_redecl.cpp
new file mode 100644
index 00000000000000..99bc521b89c13c
--- /dev/null
+++ b/clang/test/SemaCXX/nullability_redecl.cpp
@@ -0,0 +1,27 @@
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -Wno-nullability-declspec %s -verify -Wnullable-to-nonnull-conversion -I%S/Inputs
+
+class Foo;
+using Foo1 = Foo _Nonnull; // expected-error{{nullability specifier '_Nonnull' cannot be applied to non-pointer type 'Foo'}}
+class _Nullable Foo;
+using Foo2 = Foo _Nonnull;
+class Foo;
+using Foo3 = Foo _Nonnull;
+
+template <class T>
+class Bar;
+using Bar1 = Bar<int> _Nonnull; // expected-error{{nullability specifier '_Nonnull' cannot be applied to non-pointer type 'Bar<int>'}}
+template <class T>
+class _Nullable Bar;
+using Bar2 = Bar<int> _Nonnull;
+template <class T>
+class Bar;
+using Bar3 = Bar<int> _Nonnull;
+
+namespace std {
+  template<class T> class unique_ptr;
+  using UP1 = unique_ptr<int> _Nonnull;
+  class X { template<class T> friend class unique_ptr; };
+  using UP2 = unique_ptr<int> _Nonnull;
+  template<class T> class unique_ptr;
+  using UP3 = unique_ptr<int> _Nonnull;
+}

>From 4af29641598022fd263f995ae548941add3de3fd Mon Sep 17 00:00:00 2001
From: Sam McCall <sam.mccall at gmail.com>
Date: Mon, 4 Nov 2024 13:03:27 +0100
Subject: [PATCH 2/2] Fix include order

---
 clang/lib/AST/Type.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/lib/AST/Type.cpp b/clang/lib/AST/Type.cpp
index a01d7be0cacc95..6bf2908e667c07 100644
--- a/clang/lib/AST/Type.cpp
+++ b/clang/lib/AST/Type.cpp
@@ -43,8 +43,8 @@
 #include "llvm/ADT/APSInt.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/FoldingSet.h"
-#include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"