[clang] [clang] Implement lifetime analysis for lifetime_capture_by(X) (PR #115921)

[Utkarsh Saxena via cfe-commits]

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@@ -3229,6 +3230,52 @@ void Sema::CheckArgAlignment(SourceLocation Loc, NamedDecl *FDecl,
         << ParamName << (FDecl != nullptr) << FDecl;
 }
 
+void Sema::checkLifetimeCaptureBy(FunctionDecl *FD, bool IsMemberFunction,
+                                  const Expr *ThisArg,
+                                  ArrayRef<const Expr *> Args) {
+  auto GetArgAt = [&](int Idx) -> Expr * {
+    if (Idx == LifetimeCaptureByAttr::GLOBAL ||
+        Idx == LifetimeCaptureByAttr::UNKNOWN)
+      return nullptr;
+    if (IsMemberFunction && Idx == 0)
+      return const_cast<Expr *>(ThisArg);
+    return const_cast<Expr *>(Args[Idx - int(IsMemberFunction)]);
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usx95 wrote:

I feel the existing code is easier to follow. 

https://github.com/llvm/llvm-project/pull/115921