QChar: make construction from integral explicit

QChar should not be convertible from any integral type except from
char16_t, short and possibly char (since it's a direct superset).

David provided the perfect example:

  if (str == 123) { ~~~ }

compiles, with 123 implicitly converted to QChar (str == "123"
was meant instead). But similarly one can construct other
scenarios where QString(123) gets accidentally used (instead of
QString::number(123)), like QString s; s += 123;.

Add a macro to revert to the implicit constructors, for backwards
compatibility.

The breaks are mostly in tests that "abuse" of integers (arithmetic,
etc.). Maybe it's time for user-defined literals for QChar/QString,
but that is left for another commit.

[ChangeLog][Potentially Source-Incompatible Changes][QChar] QChar
constructors from integral types are now by default explicit.
It is recommended to use explicit conversions, QLatin1Char,
QChar::fromUcs4 instead of implicit conversions. The old behavior
can be restored by defining the QT_IMPLICIT_QCHAR_CONSTRUCTION
macro.

Change-Id: I6175f6ab9bcf1956f6f97ab0c9d9d5aaf777296d
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 2 insertions, 2 deletions

diff --git a/tests/auto/corelib/itemmodels/qsortfilterproxymodel_common/tst_qsortfilterproxymodel.cpp b/tests/auto/corelib/itemmodels/qsortfilterproxymodel_common/tst_qsortfilterproxymodel.cpp
index 78749559b5..20fc5d492d 100644
--- a/tests/auto/corelib/itemmodels/qsortfilterproxymodel_common/tst_qsortfilterproxymodel.cpp
+++ b/tests/auto/corelib/itemmodels/qsortfilterproxymodel_common/tst_qsortfilterproxymodel.cpp
@@ -4794,7 +4794,7 @@ void tst_QSortFilterProxyModel::filterAndInsertColumn()
     model.insertRows(0, 1);
     for (int i = 0; i < model.rowCount(); ++i) {
         for (int j = 0; j < model.columnCount(); ++j)
-            model.setData(model.index(i, j), QString('A' + j) + QString::number(i + 1));
+            model.setData(model.index(i, j), QString(QChar('A' + j)) + QString::number(i + 1));
     }
     ColumnFilterProxy proxy(filterMode);
     proxy.setSourceModel(&model);
@@ -5048,7 +5048,7 @@ void tst_QSortFilterProxyModel::invalidateColumnsOrRowsFilter()
     QStandardItemModel model(10, 4);
     for (int i = 0; i < model.rowCount(); ++i) {
         for (int j = 0; j < model.columnCount(); ++j) {
-            model.setItem(i, j, new QStandardItem(QString('A' + j) + QString::number(i + 1)));
+            model.setItem(i, j, new QStandardItem(QString(QChar('A' + j)) + QString::number(i + 1)));
             model.item(i, 0)->appendColumn({ new QStandardItem(QString("child col %0").arg(j)) });
         }
     }