[clang] [LifetimeSafety] Infer [[clang::lifetimebound]] annotation (PR #171081)

[Utkarsh Saxena via cfe-commits]

================
@@ -160,6 +162,19 @@ class LifetimeChecker {
     for (const auto &[PVD, EscapeExpr] : AnnotationWarningsMap)
       Reporter->suggestAnnotation(PVD, EscapeExpr);
   }
+
+  void inferAnnotations() {
+    /// NOTE: This currently only adds the attribute to the function definition
+    /// being analyzed. For full inter-procedural inference to work reliably
+    /// (e.g., with out-of-order definitions), this attribute would also need to
+    /// be added to all other redeclarations of the function.
----------------
usx95 wrote:

I would skip mentioning inter-procedural inference as a single clang invocation can never achieve this. I would just mention the function analysis order for best results.

`// FIXME: To maximise inference propagation, functions should be analyzed in post-order of the call hierarchy, allowing inferred annotations to propagate through the call chain.`

For issue with redecl, I think we should have a separate fixme:  
`// FIXME: Add the inferred attribute to all redeclarations of the function, not just the definition being analyzed.`

https://github.com/llvm/llvm-project/pull/171081