QScopeGuard: Make constructor public

With Class Template Argument Deduction users might want to use the constructor
itself instead of a separate helper function. In both cases it's possible to let
the compiler deduce the template arguments.

Try to make the usefulness of the helper function in the absence of CTAD still
clear in the documentation.

Change-Id: I9b07983c1fb276a6dd9e7ed4c3e606764e9b68ca
Reviewed-by: Ville Voutilainen <ville.voutilainen@qt.io>

2 files changed, 100 insertions, 6 deletions

diff --git a/tests/auto/corelib/tools/qscopeguard/qscopeguard.pro b/tests/auto/corelib/tools/qscopeguard/qscopeguard.pro
index 070d4b077c..e3645befcf 100644
--- a/tests/auto/corelib/tools/qscopeguard/qscopeguard.pro
+++ b/tests/auto/corelib/tools/qscopeguard/qscopeguard.pro
@@ -2,3 +2,6 @@ CONFIG += testcase
 TARGET = tst_qscopeguard
 QT = core testlib
 SOURCES = tst_qscopeguard.cpp
+
+# Force C++17 if available
+contains(QT_CONFIG, c++1z): CONFIG += c++1z
diff --git a/tests/auto/corelib/tools/qscopeguard/tst_qscopeguard.cpp b/tests/auto/corelib/tools/qscopeguard/tst_qscopeguard.cpp
index 01181ce20e..24c3023183 100644
--- a/tests/auto/corelib/tools/qscopeguard/tst_qscopeguard.cpp
+++ b/tests/auto/corelib/tools/qscopeguard/tst_qscopeguard.cpp
@@ -1,6 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2018 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Sérgio Martins <sergio.martins@kdab.com>
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the test suite of the Qt Toolkit.
@@ -30,24 +31,114 @@
 #include <QtCore/QScopeGuard>
 
 /*!
- \class tst_QScopedGuard
+ \class tst_QScopeGuard
  \internal
  \since 5.11
- \brief Tests class QScopedCleanup and function qScopeGuard
+ \brief Tests class QScopeGuard and function qScopeGuard
 
  */
-class tst_QScopedGuard : public QObject
+class tst_QScopeGuard : public QObject
 {
     Q_OBJECT
 
 private Q_SLOTS:
+    void construction();
+    void constructionFromLvalue();
+    void constructionFromRvalue();
     void leavingScope();
     void exceptions();
 };
 
+void func()
+{
+}
+
+int intFunc()
+{
+    return 0;
+}
+
+Q_REQUIRED_RESULT int noDiscardFunc()
+{
+    return 0;
+}
+
+struct Callable
+{
+    Callable() { }
+    Callable(const Callable &other)
+    {
+        Q_UNUSED(other);
+        ++copied;
+    }
+    Callable(Callable &&other)
+    {
+        Q_UNUSED(other);
+        ++moved;
+    }
+    void operator()() { }
+
+    static int copied;
+    static int moved;
+    static void resetCounts()
+    {
+        copied = 0;
+        moved = 0;
+    }
+};
+
+int Callable::copied = 0;
+int Callable::moved = 0;
+
 static int s_globalState = 0;
 
-void tst_QScopedGuard::leavingScope()
+void tst_QScopeGuard::construction()
+{
+#ifdef __cpp_deduction_guides
+    QScopeGuard fromLambda([] { });
+    QScopeGuard fromFunction(func);
+    QScopeGuard fromFunctionPointer(&func);
+    QScopeGuard fromNonVoidFunction(intFunc);
+    QScopeGuard fromNoDiscardFunction(noDiscardFunc);
+    QScopeGuard fromStdFunction{std::function(func)};
+    std::function stdFunction(func);
+    QScopeGuard fromNamedStdFunction(stdFunction);
+#else
+    QSKIP("This test requires C++17 Class Template Argument Deduction support enabled in the compiler.");
+#endif
+}
+
+void tst_QScopeGuard::constructionFromLvalue()
+{
+#ifdef __cpp_deduction_guides
+    Callable::resetCounts();
+    Callable callable;
+    {
+        QScopeGuard guard(callable);
+    }
+    QCOMPARE(Callable::copied, 1);
+    QCOMPARE(Callable::moved, 0);
+#else
+    QSKIP("This test requires C++17 Class Template Argument Deduction support enabled in the compiler.");
+#endif
+}
+
+void tst_QScopeGuard::constructionFromRvalue()
+{
+#ifdef __cpp_deduction_guides
+    Callable::resetCounts();
+    {
+        Callable callable;
+        QScopeGuard guard(std::move(callable));
+    }
+    QCOMPARE(Callable::copied, 0);
+    QCOMPARE(Callable::moved, 1);
+#else
+    QSKIP("This test requires C++17 Class Template Argument Deduction support enabled in the compiler.");
+#endif
+}
+
+void tst_QScopeGuard::leavingScope()
 {
     auto cleanup = qScopeGuard([] { s_globalState++; QCOMPARE(s_globalState, 3); });
     QCOMPARE(s_globalState, 0);
@@ -61,7 +152,7 @@ void tst_QScopedGuard::leavingScope()
     s_globalState++;
 }
 
-void tst_QScopedGuard::exceptions()
+void tst_QScopeGuard::exceptions()
 {
     s_globalState = 0;
     bool caught = false;
@@ -81,5 +172,5 @@ void tst_QScopedGuard::exceptions()
 
 }
 
-QTEST_MAIN(tst_QScopedGuard)
+QTEST_MAIN(tst_QScopeGuard)
 #include "tst_qscopeguard.moc"