From f732833eaa4b9beca5d9cc742af59ff80edacfe3 Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Mon, 5 Jun 2023 07:38:55 +0200
Subject: [PATCH] tst_QScopeGuard: test if and how guard in optional<> works

It's a bit cumbersome, but works, in principle, using CTAD.

Task-number: QTBUG-114200
Change-Id: Ib7354180e870a695a978edabf684aedfcf9d9ecc
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>
(cherry picked from commit b08ddd2c4ecedccd0bc08e9f2390a7b86ed861f4)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 .../tools/qscopeguard/tst_qscopeguard.cpp     | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tests/auto/corelib/tools/qscopeguard/tst_qscopeguard.cpp b/tests/auto/corelib/tools/qscopeguard/tst_qscopeguard.cpp
index 015cbcc0e74..ac6551645f7 100644
--- a/tests/auto/corelib/tools/qscopeguard/tst_qscopeguard.cpp
+++ b/tests/auto/corelib/tools/qscopeguard/tst_qscopeguard.cpp
@@ -5,6 +5,8 @@
 #include <QTest>
 #include <QtCore/QScopeGuard>
 
+#include <optional>
+
 /*!
  \class tst_QScopeGuard
  \internal
@@ -20,6 +22,7 @@ private Q_SLOTS:
     void construction();
     void constructionFromLvalue();
     void constructionFromRvalue();
+    void optionalGuard();
     void leavingScope();
     void exceptions();
 };
@@ -117,6 +120,24 @@ void tst_QScopeGuard::constructionFromRvalue()
     QCOMPARE(Callable::moved, 1);
 }
 
+void tst_QScopeGuard::optionalGuard()
+{
+    int i = 0;
+    auto lambda = [&] { ++i; };
+    std::optional sg = false ? std::optional{qScopeGuard(lambda)} : std::nullopt;
+    QVERIFY(!sg);
+    QCOMPARE(i, 0);
+    sg.emplace(qScopeGuard(lambda));
+    QVERIFY(sg);
+    sg->dismiss();
+    sg.reset();
+    QCOMPARE(i, 0);
+    sg.emplace(qScopeGuard(lambda));
+    QCOMPARE(i, 0);
+    sg.reset();
+    QCOMPARE(i, 1);
+}
+
 void tst_QScopeGuard::leavingScope()
 {
     auto cleanup = qScopeGuard([] { s_globalState++; QCOMPARE(s_globalState, 3); });