[clang] Fix null dereference on return in lambda attribute statement expr

[pfusik]

Summary

Fixes https://github.com/llvm/llvm-project/issues/48527

[pfusik]

Moved to https://github.com/llvm/llvm-project/pull/66643

clang/lib/Sema/SemaStmt.cpp

StmtResult Sema::ActOnCapScopeReturnStmt(SourceLocation ReturnLoc,
                                          Expr *RetValExp,
                                          NamedReturnInfo &NRInfo,
                                          bool SupressSimplerImplicitMoves) {
   // If this is the first return we've seen, infer the return type.
   // [expr.prim.lambda]p4 in C++11; block literals follow the same rules.
   CapturingScopeInfo *CurCap = cast<CapturingScopeInfo>(getCurFunction());
   QualType FnRetType = CurCap->ReturnType;
   LambdaScopeInfo *CurLambda = dyn_cast<LambdaScopeInfo>(CurCap);
+  if (CurLambda && CurLambda->CallOperator->getType().isNull())
+    return StmtError();
   bool HasDeducedReturnType =
       CurLambda && hasDeducedReturnType(CurLambda->CallOperator);
 
   if (ExprEvalContexts.back().isDiscardedStatementContext() &&
       (HasDeducedReturnType || CurCap->HasImplicitReturnType)) {
     if (RetValExp) {
       ExprResult ER =
           ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/ false);

clang/test/SemaCXX/gh48527.cpp

+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+int main() { // expected-note {{to match this '{'}}
+    auto a = [](void)__attribute__((b(({ // expected-note {{to match this '('}}
+    return 0;
+} // expected-error 3 {{expected ')'}} \
+  // expected-error {{expected ';' at end of declaration}}
+// expected-error@+2 {{expected ')'}}
+// expected-error@+1 {{expected body of lambda expression}}
+// expected-error {{expected '}'}}