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

[Corentin Jabot via cfe-commits]

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@@ -4469,6 +4469,52 @@ 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) {
+  if (!TSI)
+    return nullptr;
+
+  for (TypeLoc TL = TSI->getTypeLoc();;) {
+    auto ATL = TL.getAsAdjusted<AttributedTypeLoc>();
+    if (!ATL)
+      break;
+    if (auto *LBAttr = ATL.getAttrAs<LifetimeBoundAttr>())
+      return LBAttr;
+    TL = ATL.getModifiedLoc();
+  }
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cor3ntin wrote:

This might be a bit too clever - I'd prefer a while(true) with a comment

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