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, 8 insertions, 8 deletions

diff --git a/tests/auto/corelib/text/qstring/tst_qstring.cpp b/tests/auto/corelib/text/qstring/tst_qstring.cpp
index 29d794490b..99f42e2815 100644
--- a/tests/auto/corelib/text/qstring/tst_qstring.cpp
+++ b/tests/auto/corelib/text/qstring/tst_qstring.cpp
@@ -3991,7 +3991,7 @@ void tst_QString::check_QTextIOStream()
 
 void tst_QString::fromRawData()
 {
-    const QChar ptr[] = { 0x1234, 0x0000 };
+    const QChar ptr[] = { QChar(0x1234), QChar(0x0000) };
     QString cstr = QString::fromRawData(ptr, 1);
     QVERIFY(!cstr.isDetached());
     QVERIFY(cstr.constData() == ptr);
@@ -4008,8 +4008,8 @@ void tst_QString::fromRawData()
 
 void tst_QString::setRawData()
 {
-    const QChar ptr[] = { 0x1234, 0x0000 };
-    const QChar ptr2[] = { 0x4321, 0x0000 };
+    const QChar ptr[] = { QChar(0x1234), QChar(0x0000) };
+    const QChar ptr2[] = { QChar(0x4321), QChar(0x0000) };
     QString cstr;
 
     // This just tests the fromRawData() fallback
@@ -4278,7 +4278,7 @@ void tst_QString::invalidToLocal8Bit_data()
     QTest::addColumn<QByteArray>("expect"); // Initial validly-converted prefix
 
     {
-        const QChar malformed[] = { 'A', 0xd800, 'B', 0 };
+        const QChar malformed[] = { 'A', QChar(0xd800), 'B', '\0' };
         const char expected[] = "A";
         QTest::newRow("LoneHighSurrogate")
             << QString(malformed, sizeof(malformed) / sizeof(QChar))
@@ -4286,28 +4286,28 @@ void tst_QString::invalidToLocal8Bit_data()
             << QByteArray(expected, sizeof(expected) / sizeof(char) - 1);
     }
     {
-        const QChar malformed[] = { 'A', 0xdc00, 'B', 0 };
+        const QChar malformed[] = { 'A', QChar(0xdc00), 'B', '\0' };
         const char expected[] = "A";
         QTest::newRow("LoneLowSurrogate")
             << QString(malformed, sizeof(malformed) / sizeof(QChar))
             << QByteArray(expected, sizeof(expected) / sizeof(char) - 1);
     }
     {
-        const QChar malformed[] = { 'A', 0xd800, 0xd801, 'B', 0 };
+        const QChar malformed[] = { 'A', QChar(0xd800), QChar(0xd801), 'B', '\0' };
         const char expected[] = "A";
         QTest::newRow("DoubleHighSurrogate")
             << QString(malformed, sizeof(malformed) / sizeof(QChar))
             << QByteArray(expected, sizeof(expected) / sizeof(char) - 1);
     }
     {
-        const QChar malformed[] = { 'A', 0xdc00, 0xdc01, 'B', 0 };
+        const QChar malformed[] = { 'A', QChar(0xdc00), QChar(0xdc01), 'B', '\0' };
         const char expected[] = "A";
         QTest::newRow("DoubleLowSurrogate")
             << QString(malformed, sizeof(malformed) / sizeof(QChar))
             << QByteArray(expected, sizeof(expected) / sizeof(char) - 1);
     }
     {
-        const QChar malformed[] = { 'A', 0xdc00, 0xd800, 'B', 0 };
+        const QChar malformed[] = { 'A', QChar(0xdc00), QChar(0xd800), 'B', '\0' };
         const char expected[] = "A";
         QTest::newRow("ReversedSurrogates") // low before high
             << QString(malformed, sizeof(malformed) / sizeof(QChar))