[clang] [coroutines][coro_lifetimebound] Detect lifetime issues with lambda captures (PR #77066)

[Ilya Biryukov via cfe-commits]

================
@@ -7575,15 +7577,27 @@ static void visitLifetimeBoundArguments(IndirectLocalPath &Path, Expr *Call,
     Path.pop_back();
   };
 
-  if (ObjectArg && implicitObjectParamIsLifetimeBound(Callee))
-    VisitLifetimeBoundArg(Callee, ObjectArg);
-
   bool CheckCoroCall = false;
   if (const auto *RD = Callee->getReturnType()->getAsRecordDecl()) {
     CheckCoroCall = RD->hasAttr<CoroLifetimeBoundAttr>() &&
                     RD->hasAttr<CoroReturnTypeAttr>() &&
                     !Callee->hasAttr<CoroDisableLifetimeBoundAttr>();
   }
+
+  if (ObjectArg) {
+    bool CheckCoroObjArg = CheckCoroCall;
+    // Ignore `__promise.get_return_object()` as it is not lifetimebound.
+    if (CheckCoroObjArg && Callee->getDeclName().isIdentifier() &&
+        Callee->getName() == "get_return_object")
+      CheckCoroObjArg = false;
+    // Coroutine lambda objects with empty capture list are not lifetimebound.
+    if (auto *LE = dyn_cast<LambdaExpr>(ObjectArg->IgnoreImplicit());
+        LE && LE->captures().empty())
+      CheckCoroObjArg = false;
----------------
ilya-biryukov wrote:

There are simple workarounds to silence these warnings in those cases:
- converting to a function pointer before call `(+[](){ ... co_await foo(); ... })()`,
- declaring a lambda as static  `[]() static { ... co_await foo(); ...}()` (starting with C++23).

https://github.com/llvm/llvm-project/pull/77066