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QStringView: add a test for overload resolution versus QString

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In the presence of multiple overloads of a function taking either
QString or QStringView, QStringView should always be preferred.

The rationale is that the QStringView overload may have been
added "later" (read: the function was written when QStringView
was not available yet, so it took QString), and the fact that
a function with the _same name_ offers a QStringView overload
implies the function never needed to store/own the string in
the first place.

Add a (compile-time) test for this preference. This is in
preparation for a future QString(char16_t*) constructor
(in Qt 5.15 / Qt 6).

Change-Id: I60a435e494b653548f8f8d52c5d7e7cac2cc875a
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Giuseppe D'Angelo 2020-01-06 18:16:37 +01:00
parent 5e66ea373a
commit 50f3ccd782
1 changed files with 58 additions and 0 deletions
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58
tests/auto/corelib/text/qstringview/tst_qstringview.cpp
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@ -221,6 +221,8 @@ private Q_SLOTS:
void comparison();
void overloadResolution();
private:
template <typename String>
void conversion_tests(String arg) const;
@ -678,5 +680,61 @@ void tst_QStringView::comparison()
QVERIFY(bb.compare(aa) > 0);
}
namespace QStringViewOverloadResolution {
static void test(QString) = delete;
static void test(QStringView) {}
}
// Compile-time only test: overload resolution prefers QStringView over QString
void tst_QStringView::overloadResolution()
{
{
QChar qcharArray[42] = {};
QStringViewOverloadResolution::test(qcharArray);
QChar *qcharPointer = qcharArray;
QStringViewOverloadResolution::test(qcharPointer);
}
{
ushort ushortArray[42] = {};
QStringViewOverloadResolution::test(ushortArray);
ushort *ushortPointer = ushortArray;
QStringViewOverloadResolution::test(ushortPointer);
}
{
QStringRef stringRef;
QStringViewOverloadResolution::test(stringRef);
QStringViewOverloadResolution::test(qAsConst(stringRef));
QStringViewOverloadResolution::test(std::move(stringRef));
}
#if defined(Q_OS_WIN)
{
wchar_t wchartArray[42] = {};
QStringViewOverloadResolution::test(wchartArray);
QStringViewOverloadResolution::test(L"test");
}
#endif
#if defined(Q_COMPILER_UNICODE_STRINGS)
{
char16_t char16Array[] = u"test";
QStringViewOverloadResolution::test(char16Array);
char16_t *char16Pointer = char16Array;
QStringViewOverloadResolution::test(char16Pointer);
}
#endif
#if defined(Q_STDLIB_UNICODE_STRINGS)
{
std::u16string string;
QStringViewOverloadResolution::test(string);
QStringViewOverloadResolution::test(qAsConst(string));
QStringViewOverloadResolution::test(std::move(string));
}
#endif
}
QTEST_APPLESS_MAIN(tst_QStringView)
#include "tst_qstringview.moc"