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>

2 files changed, 5 insertions, 5 deletions

diff --git a/tests/auto/corelib/serialization/json/tst_qtjson.cpp b/tests/auto/corelib/serialization/json/tst_qtjson.cpp
index 5d4a9b15b1..04411cea63 100644
--- a/tests/auto/corelib/serialization/json/tst_qtjson.cpp
+++ b/tests/auto/corelib/serialization/json/tst_qtjson.cpp
@@ -3229,8 +3229,8 @@ void tst_QtJson::streamSerializationQJsonValue_data()
     QTest::newRow("array") << QJsonValue{QJsonArray{12,1,5,6,7}};
     QTest::newRow("object") << QJsonValue{QJsonObject{{"foo", 665}, {"bar", 666}}};
     // test json escape sequence
-    QTest::newRow("array with 0xD800") << QJsonValue(QJsonArray{QString(0xD800)});
-    QTest::newRow("array with 0xDF06,0xD834") << QJsonValue(QJsonArray{QString(0xDF06).append(0xD834)});
+    QTest::newRow("array with 0xD800") << QJsonValue(QJsonArray{QString(QChar(0xD800))});
+    QTest::newRow("array with 0xDF06,0xD834") << QJsonValue(QJsonArray{QString(QChar(0xDF06)).append(QChar(0xD834))});
 }
 
 void tst_QtJson::streamSerializationQJsonValue()
@@ -3323,8 +3323,8 @@ void tst_QtJson::escapeSurrogateCodePoints_data()
 {
     QTest::addColumn<QString>("str");
     QTest::addColumn<QByteArray>("escStr");
-    QTest::newRow("0xD800") << QString(0xD800) << QByteArray("\\ud800");
-    QTest::newRow("0xDF06,0xD834") << QString(0xDF06).append(0xD834) << QByteArray("\\udf06\\ud834");
+    QTest::newRow("0xD800") << QString(QChar(0xD800)) << QByteArray("\\ud800");
+    QTest::newRow("0xDF06,0xD834") << QString(QChar(0xDF06)).append(QChar(0xD834)) << QByteArray("\\udf06\\ud834");
 }
 
 void tst_QtJson::escapeSurrogateCodePoints()
diff --git a/tests/auto/corelib/serialization/qdatastream/tst_qdatastream.cpp b/tests/auto/corelib/serialization/qdatastream/tst_qdatastream.cpp
index 7249e2a6d8..b0fddf171e 100644
--- a/tests/auto/corelib/serialization/qdatastream/tst_qdatastream.cpp
+++ b/tests/auto/corelib/serialization/qdatastream/tst_qdatastream.cpp
@@ -2874,7 +2874,7 @@ void tst_QDataStream::status_QString_data()
     QString oneMbMinus1;
     oneMbMinus1.resize(1024 * 1024 - 1);
     for (int i = 0; i < oneMbMinus1.size(); ++i)
-        oneMbMinus1[i] = 0x1 | (8 * ((uchar)i / 9));
+        oneMbMinus1[i] = QChar(0x1 | (8 * ((uchar)i / 9)));
     QString threeMbMinus1 = oneMbMinus1 + QChar('j') + oneMbMinus1 + QChar('k') + oneMbMinus1;
 
     QByteArray threeMbMinus1Data = qstring2qbytearray(threeMbMinus1);