[clang] [Clang] FunctionEffects: ignore (methods of) local CXXRecordDecls. (PR #166078)

[Doug Wyatt via cfe-commits]

https://github.com/dougsonos created https://github.com/llvm/llvm-project/pull/166078

In the following example, `Functor::method()` inappropriately triggers a diagnostic that `outer()` is blocking by allocating memory.

```
void outer() [[clang::nonblocking]]
{
	struct Functor {
		int* ptr;
		
		void method() { ptr = new int; }
	};
```

>From 293536100d9fb8fd1dea281866502f22ac2de506 Mon Sep 17 00:00:00 2001
From: Doug Wyatt <dwyatt at apple.com>
Date: Sun, 2 Nov 2025 09:04:14 -0800
Subject: [PATCH] [Clang] FunctionEffects: ignore (methods of) local
 CXXRecordDecls.

---
 clang/lib/Sema/SemaFunctionEffects.cpp           | 8 ++++++++
 clang/test/Sema/attr-nonblocking-constraints.cpp | 9 +++++++++
 2 files changed, 17 insertions(+)

diff --git a/clang/lib/Sema/SemaFunctionEffects.cpp b/clang/lib/Sema/SemaFunctionEffects.cpp
index 8590ee831084f..7ae8d909aa337 100644
--- a/clang/lib/Sema/SemaFunctionEffects.cpp
+++ b/clang/lib/Sema/SemaFunctionEffects.cpp
@@ -1286,6 +1286,14 @@ class Analyzer {
       return true;
     }
 
+    bool TraverseCXXRecordDecl(CXXRecordDecl *D) override {
+      // Completely skip local struct/class/union declarations since their
+      // methods would otherwise be incorrectly interpreted as part of the
+      // function we are currently traversing. The initial Sema pass will have
+      // already recorded any nonblocking methods needing analysis.
+      return true;
+    }
+
     bool TraverseConstructorInitializer(CXXCtorInitializer *Init) override {
       ViolationSite PrevVS = VSite;
       if (Init->isAnyMemberInitializer())
diff --git a/clang/test/Sema/attr-nonblocking-constraints.cpp b/clang/test/Sema/attr-nonblocking-constraints.cpp
index b26a945843696..e75d2967e4927 100644
--- a/clang/test/Sema/attr-nonblocking-constraints.cpp
+++ b/clang/test/Sema/attr-nonblocking-constraints.cpp
@@ -104,6 +104,15 @@ void nb8c()
 	};
 }
 
+void nb8d() [[clang::nonblocking]]
+{
+	// Blocking methods of a local CXXRecordDecl do not generate diagnostics
+	// for the outer function.
+	struct Functor1 {
+        void method() { void* ptr = new int; }
+	};
+}
+
 // Make sure template expansions are found and verified.
 	template <typename T>
 	struct Adder {