[clang] [clang] Fix a crash when a variable is captured by a block nested inside a lambda (PR #93749)

[Akira Hatanaka via cfe-commits]

https://github.com/ahatanak updated https://github.com/llvm/llvm-project/pull/93749

>From 4648f46f5e15d5747596347feaef85069a8ce4df Mon Sep 17 00:00:00 2001
From: Akira Hatanaka <ahatanak at gmail.com>
Date: Wed, 29 May 2024 15:19:58 -0700
Subject: [PATCH 1/3] Use cast_or_null instead of cast

`Eval->Value.get` returns a null pointer when the variable doesn't have
an initializer.

This fixes https://github.com/llvm/llvm-project/issues/93625.

rdar://128482541
---
 clang/lib/AST/Decl.cpp                 |  8 +++++---
 clang/test/SemaObjCXX/block-capture.mm | 18 ++++++++++++++++++
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 41fbfe281ef65..4940a787e7d30 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -2408,9 +2408,11 @@ Expr *VarDecl::getInit() {
     return cast<Expr>(S);
 
   auto *Eval = getEvaluatedStmt();
-  return cast<Expr>(Eval->Value.isOffset()
-                        ? Eval->Value.get(getASTContext().getExternalSource())
-                        : Eval->Value.get(nullptr));
+
+  return cast_or_null<Expr>(
+      Eval->Value.isOffset()
+          ? Eval->Value.get(getASTContext().getExternalSource())
+          : Eval->Value.get(nullptr));
 }
 
 Stmt **VarDecl::getInitAddress() {
diff --git a/clang/test/SemaObjCXX/block-capture.mm b/clang/test/SemaObjCXX/block-capture.mm
index 8ba02f919e015..231aef33f2c7e 100644
--- a/clang/test/SemaObjCXX/block-capture.mm
+++ b/clang/test/SemaObjCXX/block-capture.mm
@@ -83,3 +83,21 @@
   SubMove(SubSubMove &&);
 };
 TEST(SubMove);
+
+
+#if __cplusplus >= 202302L
+// clang used to crash compiling this code.
+namespace BlockInLambda {
+  struct S {
+    constexpr ~S();
+  };
+
+  void func(S const &a) {
+    [a](auto b) {
+      ^{
+        (void)a;
+      }();
+    }(12);
+  }
+}
+#endif

>From de2bd511b5dcd683b762b7bc68f8628de30f3341 Mon Sep 17 00:00:00 2001
From: Akira Hatanaka <ahatanak at gmail.com>
Date: Thu, 30 May 2024 09:12:49 -0700
Subject: [PATCH 2/3] Use cast_if_present

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

diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 4940a787e7d30..0a35ed536a6a7 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -2409,7 +2409,7 @@ Expr *VarDecl::getInit() {
 
   auto *Eval = getEvaluatedStmt();
 
-  return cast_or_null<Expr>(
+  return cast_if_present<Expr>(
       Eval->Value.isOffset()
           ? Eval->Value.get(getASTContext().getExternalSource())
           : Eval->Value.get(nullptr));

>From 23908d596741b271feb70feb6291bc5b8a5ed97b Mon Sep 17 00:00:00 2001
From: Akira Hatanaka <ahatanak at gmail.com>
Date: Thu, 30 May 2024 10:06:47 -0700
Subject: [PATCH 3/3] Add an entry in release note

---
 clang/docs/ReleaseNotes.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 44035f48cb3f9..0d9e4b8aba500 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -813,6 +813,7 @@ Bug Fixes to C++ Support
 - Clang now allows ``@$``` in raw string literals. Fixes (#GH93130).
 - Fix an assertion failure when checking invalid ``this`` usage in the wrong context. (Fixes #GH91536).
 - Clang no longer models dependent NTTP arguments as ``TemplateParamObjectDecl`` s. Fixes (#GH84052).
+- Fix a crash when a variable is captured by a block nested inside a lambda. (Fixes #GH93625).
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^