[clang] [LifetimeSafety] Merge lifetimebound attribute on implicit 'this' across method redeclarations (PR #172146)

[Gábor Horváth via cfe-commits]

================
@@ -4469,6 +4469,53 @@ bool Sema::MergeFunctionDecl(FunctionDecl *New, NamedDecl *&OldD, Scope *S,
   return true;
 }
 
+/// Check if a function has a lifetimebound attribute on its function type
+/// (which represents the implicit 'this' parameter for methods).
+/// Returns the attribute if found, nullptr otherwise.
+static const LifetimeBoundAttr *
+getLifetimeBoundAttrFromType(const TypeSourceInfo *TSI) {
----------------
Xazax-hun wrote:

Don't we have a very similar function somewhere else? Could we deduplicate this?

https://github.com/llvm/llvm-project/pull/172146