QDate(Time)?::fromString(): do not use QCalendar as a default argument

QCalendar is not a trivial type, so using it as a default argument in
various fromString() overloads introduces an extra overhead.

In this case the function actually always needs a QCalendar object,
and a default-constructed QCalendar reproduces a valid gregorian
calendar. But getting rid of a default argument still gives us the
benefit of constructing the object only in the library, not at every
call site.
So, split each overload into two - with and without a QCalendar
argument.

Amends 41f84f3ddb780ec751e3fc706dd242fc4a99de7a

Found in 6.7 API review

Pick-to: 6.7
Change-Id: I7329276cbda0e5471dc5348af92fc8c9ca4e0738
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Marc Mutz <marc.mutz@qt.io>

2 files changed, 76 insertions, 12 deletions

diff --git a/src/corelib/time/qdatetime.cpp b/src/corelib/time/qdatetime.cpp
index cdb88a72d5..1f401948cc 100644
--- a/src/corelib/time/qdatetime.cpp
+++ b/src/corelib/time/qdatetime.cpp
@@ -1844,6 +1844,33 @@ QDate QDate::fromString(const QString &string, QStringView format, int baseYear,
     \overload
     \since 6.7
 */
+
+/*!
+    \fn QDate QDate::fromString(QStringView string, QStringView format, int baseYear)
+    \overload
+    \since 6.7
+
+    Uses a default-constructed QCalendar.
+*/
+
+/*!
+    \overload
+    \since 6.7
+
+    Uses a default-constructed QCalendar.
+*/
+QDate QDate::fromString(const QString &string, QStringView format, int baseYear)
+{
+    return fromString(string, format, baseYear, QCalendar());
+}
+
+/*!
+    \fn QDate QDate::fromString(const QString &string, const QString &format, int baseYear)
+    \overload
+    \since 6.7
+
+    Uses a default-constructed QCalendar.
+*/
 #endif // datestring
 
 /*!
@@ -5848,6 +5875,33 @@ QDateTime QDateTime::fromString(const QString &string, QStringView format, int b
     \overload
     \since 6.7
 */
+
+/*!
+    \fn QDateTime QDateTime::fromString(QStringView string, QStringView format, int baseYear)
+    \overload
+    \since 6.7
+
+    Uses a default-constructed QCalendar.
+*/
+
+/*!
+    \overload
+    \since 6.7
+
+    Uses a default-constructed QCalendar.
+*/
+QDateTime QDateTime::fromString(const QString &string, QStringView format, int baseYear)
+{
+    return fromString(string, format, baseYear, QCalendar());
+}
+
+/*!
+    \fn QDateTime QDateTime::fromString(const QString &string, const QString &format, int baseYear)
+    \overload
+    \since 6.7
+
+    Uses a default-constructed QCalendar.
+*/
 #endif // datestring
 
 /*****************************************************************************
diff --git a/src/corelib/time/qdatetime.h b/src/corelib/time/qdatetime.h
index 518705fca7..cec7771a8d 100644
--- a/src/corelib/time/qdatetime.h
+++ b/src/corelib/time/qdatetime.h
@@ -144,15 +144,20 @@ public:
     // Overriding base year is likely more common than overriding calendar (and
     // likely to get more so, as the legacy base drops ever further behind us).
     static QDate fromString(QStringView string, QStringView format,
-                            int baseYear = QLocale::DefaultTwoDigitBaseYear,
-                            QCalendar cal = QCalendar())
+                            int baseYear = QLocale::DefaultTwoDigitBaseYear)
+    { return fromString(string.toString(), format, baseYear); }
+    static QDate fromString(QStringView string, QStringView format,
+                            int baseYear, QCalendar cal)
     { return fromString(string.toString(), format, baseYear, cal); }
     static QDate fromString(const QString &string, QStringView format,
-                            int baseYear = QLocale::DefaultTwoDigitBaseYear,
-                            QCalendar cal = QCalendar());
+                            int baseYear = QLocale::DefaultTwoDigitBaseYear);
+    static QDate fromString(const QString &string, QStringView format,
+                            int baseYear, QCalendar cal);
+    static QDate fromString(const QString &string, const QString &format,
+                            int baseYear = QLocale::DefaultTwoDigitBaseYear)
+    { return fromString(string, qToStringViewIgnoringNull(format), baseYear); }
     static QDate fromString(const QString &string, const QString &format,
-                            int baseYear = QLocale::DefaultTwoDigitBaseYear,
-                            QCalendar cal = QCalendar())
+                            int baseYear, QCalendar cal)
     { return fromString(string, qToStringViewIgnoringNull(format), baseYear, cal); }
 #endif
     static bool isValid(int y, int m, int d);
@@ -451,15 +456,20 @@ public:
     // Overriding base year is likely more common than overriding calendar (and
     // likely to get more so, as the legacy base drops ever further behind us).
     static QDateTime fromString(QStringView string, QStringView format,
-                                int baseYear = QLocale::DefaultTwoDigitBaseYear,
-                                QCalendar cal = QCalendar())
+                                int baseYear = QLocale::DefaultTwoDigitBaseYear)
+    { return fromString(string.toString(), format, baseYear); }
+    static QDateTime fromString(QStringView string, QStringView format,
+                                int baseYear, QCalendar cal)
     { return fromString(string.toString(), format, baseYear, cal); }
     static QDateTime fromString(const QString &string, QStringView format,
-                                int baseYear = QLocale::DefaultTwoDigitBaseYear,
-                                QCalendar cal = QCalendar());
+                                int baseYear = QLocale::DefaultTwoDigitBaseYear);
+    static QDateTime fromString(const QString &string, QStringView format,
+                                int baseYear, QCalendar cal);
+    static QDateTime fromString(const QString &string, const QString &format,
+                                int baseYear = QLocale::DefaultTwoDigitBaseYear)
+    { return fromString(string, qToStringViewIgnoringNull(format), baseYear); }
     static QDateTime fromString(const QString &string, const QString &format,
-                                int baseYear = QLocale::DefaultTwoDigitBaseYear,
-                                QCalendar cal = QCalendar())
+                                int baseYear, QCalendar cal)
     { return fromString(string, qToStringViewIgnoringNull(format), baseYear, cal); }
 #endif