[clang] [clang] Fix the post-filtering heuristic for GSLPointer. (PR #114044)

[Gábor Horváth via cfe-commits]

================
@@ -1093,6 +1093,87 @@ static bool pathOnlyHandlesGslPointer(const IndirectLocalPath &Path) {
   }
   return false;
 }
+// Result of analyzing the Path for GSLPointer.
+enum AnalysisResult {
+  // Path does not correspond to a GSLPointer.
+  NotGSLPointer,
+
+  // A relevant case was identified.
+  Report,
+  // Stop the entire traversal.
+  Abandon,
+  // Skip this step and continue traversing inner AST nodes.
+  Skip,
+};
+// Analyze cases where a GSLPointer is initialized or assigned from a
+// temporary owner object.
+static AnalysisResult analyzePathForGSLPointer(const IndirectLocalPath &Path,
+                                               Local L) {
+  if (!pathOnlyHandlesGslPointer(Path))
+    return NotGSLPointer;
+
+  // At this point, Path represents a series of operations involving a
+  // GSLPointer, either in the process of initialization or assignment.
+
+  // Note: A LifetimeBoundCall can appear interleaved in this sequence.
+  // For example:
+  //    const std::string& Ref(const std::string& a [[clang::lifetimebound]]);
+  //    string_view abc = Ref(std::string());
+  // The "Path" is [GSLPointerInit, LifetimeboundCall], where "L" is the
+  // temporary "std::string()" object. We need to check if the function with the
+  // lifetimebound attribute returns a "owner" type.
+  if (Path.back().Kind == IndirectLocalPathEntry::LifetimeBoundCall) {
+    // The lifetimebound applies to the implicit object parameter of a method.
+    if (const auto *Method = llvm::dyn_cast<CXXMethodDecl>(Path.back().D)) {
+      if (Method->getReturnType()->isReferenceType() &&
----------------
Xazax-hun wrote:

This branch looks identical to the `FunctionDecl` case. I am wondering if we just need to set up `FD` to either be `Path.back().D` or `PD->getDeclContext()` and the code below would handle the implicit object parameter case properly.

https://github.com/llvm/llvm-project/pull/114044