QVariant: Add support for in-place construction

This avoids constructing an object just to copy (later: move) it into a
QVariant.
ChangeLog will be in a follow-up change adding emplace support.

Task-number: QTBUG-112187
Change-Id: I444e580c7d8927d41b3d21d5a521e7c475119e4c
Reviewed-by: Marc Mutz <marc.mutz@qt.io>

1 files changed, 19 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp b/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
index 6667d95e0d..698d117f70 100644
--- a/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
+++ b/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
@@ -378,6 +378,8 @@ private slots:
     void constructFromIncompatibleMetaType();
     void copyNonDefaultConstructible();
 
+    void inplaceConstruct();
+
     void getIf_int() { getIf_impl(42); }
     void getIf_QString() { getIf_impl(u"string"_s); };
     void getIf_NonDefaultConstructible();
@@ -5720,6 +5722,23 @@ void tst_QVariant::copyNonDefaultConstructible()
     QCOMPARE(var2, var);
 }
 
+void tst_QVariant::inplaceConstruct()
+{
+    {
+        NonDefaultConstructible ndc(42);
+        QVariant var(std::in_place_type<NonDefaultConstructible>, 42);
+        QVERIFY(get_if<NonDefaultConstructible>(&var));
+        QCOMPARE(get<NonDefaultConstructible>(var), ndc);
+    }
+
+    {
+        std::vector<int> vec {1, 2, 3, 4};
+        QVariant var(std::in_place_type<std::vector<int>>, {1, 2, 3, 4});
+        QVERIFY(get_if<std::vector<int>>(&var));
+        QCOMPARE(get<std::vector<int>>(var), vec);
+    }
+}
+
 void tst_QVariant::getIf_NonDefaultConstructible()
 {
     getIf_impl(NonDefaultConstructible{42});