Be less laissez-faire with implicit conversions to QChar

QChar currently is convertible from nearly every integral type. This
is bad code hygiene and should be fixed come Qt 6.

The present patch is the result of compile fixes from marking these
constructors explicit. As is clear from the distribution of fixes,
only low-level string handling code used these implicit conversions,
an indication that they're not in widespread use elsewhere.

Change-Id: Ief5336f21e6d181e03ab92893b3d13a14adc7cb0
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

17 files changed, 60 insertions, 61 deletions

diff --git a/src/corelib/codecs/qlatincodec.cpp b/src/corelib/codecs/qlatincodec.cpp
index 463c5a56ae..55e6f0ba4d 100644
--- a/src/corelib/codecs/qlatincodec.cpp
+++ b/src/corelib/codecs/qlatincodec.cpp
@@ -62,7 +62,7 @@ QByteArray QLatin1Codec::convertFromUnicode(const QChar *ch, int len, ConverterS
     char *d = r.data();
     int invalid = 0;
     for (int i = 0; i < len; ++i) {
-        if (ch[i] > 0xff) {
+        if (ch[i] > QChar(0xff)) {
             d[i] = replacement;
             ++invalid;
         } else {
@@ -112,28 +112,28 @@ QString QLatin15Codec::convertToUnicode(const char* chars, int len, ConverterSta
     while(len--) {
         switch(uc->unicode()) {
             case 0xa4:
-                *uc = 0x20ac;
+                *uc = QChar(0x20ac);
                 break;
             case 0xa6:
-                *uc = 0x0160;
+                *uc = QChar(0x0160);
                 break;
             case 0xa8:
-                *uc = 0x0161;
+                *uc = QChar(0x0161);
                 break;
             case 0xb4:
-                *uc = 0x017d;
+                *uc = QChar(0x017d);
                 break;
             case 0xb8:
-                *uc = 0x017e;
+                *uc = QChar(0x017e);
                 break;
             case 0xbc:
-                *uc = 0x0152;
+                *uc = QChar(0x0152);
                 break;
             case 0xbd:
-                *uc = 0x0153;
+                *uc = QChar(0x0153);
                 break;
             case 0xbe:
-                *uc = 0x0178;
+                *uc = QChar(0x0178);
                 break;
             default:
                 break;
diff --git a/src/corelib/codecs/qutfcodec.cpp b/src/corelib/codecs/qutfcodec.cpp
index 85736fdf02..af36bd7e2f 100644
--- a/src/corelib/codecs/qutfcodec.cpp
+++ b/src/corelib/codecs/qutfcodec.cpp
@@ -951,10 +951,10 @@ QString QUtf32::convertToUnicode(const char *chars, int len, QTextCodec::Convert
             }
             uint code = (endian == BigEndianness) ? qFromBigEndian<quint32>(tuple) : qFromLittleEndian<quint32>(tuple);
             if (QChar::requiresSurrogates(code)) {
-                *qch++ = QChar::highSurrogate(code);
-                *qch++ = QChar::lowSurrogate(code);
+                *qch++ = QChar(QChar::highSurrogate(code));
+                *qch++ = QChar(QChar::lowSurrogate(code));
             } else {
-                *qch++ = code;
+                *qch++ = QChar(code);
             }
             num = 0;
         }
diff --git a/src/corelib/io/qdir_p.h b/src/corelib/io/qdir_p.h
index 0f3ab7f899..42218e1ccf 100644
--- a/src/corelib/io/qdir_p.h
+++ b/src/corelib/io/qdir_p.h
@@ -82,7 +82,7 @@ public:
 
     static inline QChar getFilterSepChar(const QString &nameFilter);
 
-    static inline QStringList splitFilters(const QString &nameFilter, QChar sep = 0);
+    static inline QStringList splitFilters(const QString &nameFilter, QChar sep = {});
 
     void setPath(const QString &path);
 
diff --git a/src/corelib/io/qipaddress.cpp b/src/corelib/io/qipaddress.cpp
index b3421fca8f..ddc5b6607f 100644
--- a/src/corelib/io/qipaddress.cpp
+++ b/src/corelib/io/qipaddress.cpp
@@ -312,7 +312,7 @@ void toString(QString &appendTo, const IPv6Address address)
         }
     }
 
-    const QChar colon = ushort(':');
+    const QChar colon = u':';
     if (zeroRunLength < 4)
         zeroRunOffset = -1;
     else if (zeroRunOffset == 0)
diff --git a/src/corelib/io/qurl.cpp b/src/corelib/io/qurl.cpp
index d9ebc6c750..878e007fb0 100644
--- a/src/corelib/io/qurl.cpp
+++ b/src/corelib/io/qurl.cpp
@@ -1010,7 +1010,7 @@ inline bool QUrlPrivate::setScheme(const QString &value, int len, bool doSetErro
         for (int i = needsLowercasing; i >= 0; --i) {
             ushort c = schemeData[i].unicode();
             if (c >= 'A' && c <= 'Z')
-                schemeData[i] = c + 0x20;
+                schemeData[i] = QChar(c + 0x20);
         }
     }
 
diff --git a/src/corelib/io/qurlidna.cpp b/src/corelib/io/qurlidna.cpp
index 2f89d22660..a2f0caa606 100644
--- a/src/corelib/io/qurlidna.cpp
+++ b/src/corelib/io/qurlidna.cpp
@@ -2220,9 +2220,8 @@ Q_AUTOTEST_EXPORT void qt_punycodeEncoder(const QChar *s, int ucLength, QString
     bool skipped = false;
     // copy all basic code points verbatim to output.
     for (uint j = 0; j < (uint) ucLength; ++j) {
-        ushort js = s[j].unicode();
-        if (js < 0x80)
-            *d++ = js;
+        if (s[j].unicode() < 0x80)
+            *d++ = s[j];
         else
             skipped = true;
     }
diff --git a/src/corelib/io/qurlquery.cpp b/src/corelib/io/qurlquery.cpp
index 36a2880bf1..e6aec9bf45 100644
--- a/src/corelib/io/qurlquery.cpp
+++ b/src/corelib/io/qurlquery.cpp
@@ -293,9 +293,9 @@ void QUrlQueryPrivate::setQuery(const QString &query)
         const QChar *delimiter = nullptr;
         while (pos != end) {
             // scan for the component parts of this pair
-            if (!delimiter && pos->unicode() == valueDelimiter)
+            if (!delimiter && *pos == valueDelimiter)
                 delimiter = pos;
-            if (pos->unicode() == pairDelimiter)
+            if (*pos == pairDelimiter)
                 break;
             ++pos;
         }
@@ -584,8 +584,8 @@ QString QUrlQuery::query(QUrl::ComponentFormattingOptions encoding) const
 */
 void QUrlQuery::setQueryDelimiters(QChar valueDelimiter, QChar pairDelimiter)
 {
-    d->valueDelimiter = valueDelimiter.unicode();
-    d->pairDelimiter = pairDelimiter.unicode();
+    d->valueDelimiter = valueDelimiter;
+    d->pairDelimiter = pairDelimiter;
 }
 
 /*!
diff --git a/src/corelib/serialization/qtextstream.cpp b/src/corelib/serialization/qtextstream.cpp
index 9d4bc223ab..a675c3cede 100644
--- a/src/corelib/serialization/qtextstream.cpp
+++ b/src/corelib/serialization/qtextstream.cpp
@@ -888,7 +888,7 @@ inline bool QTextStreamPrivate::getChar(QChar *ch)
     if ((string && stringOffset == string->size())
         || (device && readBuffer.isEmpty() && !fillReadBuffer())) {
         if (ch)
-            *ch = 0;
+            *ch = QChar();
         return false;
     }
     if (ch)
diff --git a/src/corelib/serialization/qxmlstream.cpp b/src/corelib/serialization/qxmlstream.cpp
index be3a476cb2..27a5137fc9 100644
--- a/src/corelib/serialization/qxmlstream.cpp
+++ b/src/corelib/serialization/qxmlstream.cpp
@@ -1423,7 +1423,7 @@ inline int QXmlStreamReaderPrivate::fastScanNMTOKEN()
     int n = 0;
     uint c;
     while ((c = getChar()) != StreamEOF) {
-        if (fastDetermineNameChar(c) == NotName) {
+        if (fastDetermineNameChar(QChar(c)) == NotName) {
             putChar(c);
             return n;
         } else {
diff --git a/src/corelib/tools/qchar.cpp b/src/corelib/tools/qchar.cpp
index e097e4a5fe..0c190c6a3d 100644
--- a/src/corelib/tools/qchar.cpp
+++ b/src/corelib/tools/qchar.cpp
@@ -1885,11 +1885,11 @@ static void composeHelper(QString *str, QChar::UnicodeVersion version, int from)
                 QChar *d = s.data();
                 // ligatureHelper() never changes planes
                 if (QChar::requiresSurrogates(ligature)) {
-                    d[starter] = QChar::highSurrogate(ligature);
-                    d[starter + 1] = QChar::lowSurrogate(ligature);
+                    d[starter] = QChar(QChar::highSurrogate(ligature));
+                    d[starter + 1] = QChar(QChar::lowSurrogate(ligature));
                     s.remove(i, 2);
                 } else {
-                    d[starter] = ligature;
+                    d[starter] = QChar(ligature);
                     s.remove(i, 1);
                 }
                 continue;
@@ -1962,16 +1962,16 @@ static void canonicalOrderHelper(QString *str, QChar::UnicodeVersion version, in
             int p = pos;
             // exchange characters
             if (!QChar::requiresSurrogates(u2)) {
-                uc[p++] = u2;
+                uc[p++] = QChar(u2);
             } else {
-                uc[p++] = QChar::highSurrogate(u2);
-                uc[p++] = QChar::lowSurrogate(u2);
+                uc[p++] = QChar(QChar::highSurrogate(u2));
+                uc[p++] = QChar(QChar::lowSurrogate(u2));
             }
             if (!QChar::requiresSurrogates(u1)) {
-                uc[p++] = u1;
+                uc[p++] = QChar(u1);
             } else {
-                uc[p++] = QChar::highSurrogate(u1);
-                uc[p++] = QChar::lowSurrogate(u1);
+                uc[p++] = QChar(QChar::highSurrogate(u1));
+                uc[p++] = QChar(QChar::lowSurrogate(u1));
             }
             if (pos > 0)
                 --pos;
diff --git a/src/corelib/tools/qchar.h b/src/corelib/tools/qchar.h
index 73344ecf52..e028a24c24 100644
--- a/src/corelib/tools/qchar.h
+++ b/src/corelib/tools/qchar.h
@@ -443,17 +443,17 @@ public:
 #endif
     inline unsigned char combiningClass() const noexcept { return QChar::combiningClass(ucs); }
 
-    inline QChar mirroredChar() const noexcept { return QChar::mirroredChar(ucs); }
+    inline QChar mirroredChar() const noexcept { return QChar(QChar::mirroredChar(ucs)); }
     inline bool hasMirrored() const noexcept { return QChar::hasMirrored(ucs); }
 
     QString decomposition() const;
     inline Decomposition decompositionTag() const noexcept { return QChar::decompositionTag(ucs); }
 
     inline int digitValue() const noexcept { return QChar::digitValue(ucs); }
-    inline QChar toLower() const noexcept { return QChar::toLower(ucs); }
-    inline QChar toUpper() const noexcept { return QChar::toUpper(ucs); }
-    inline QChar toTitleCase() const noexcept { return QChar::toTitleCase(ucs); }
-    inline QChar toCaseFolded() const noexcept { return QChar::toCaseFolded(ucs); }
+    inline QChar toLower() const noexcept { return QChar(QChar::toLower(ucs)); }
+    inline QChar toUpper() const noexcept { return QChar(QChar::toUpper(ucs)); }
+    inline QChar toTitleCase() const noexcept { return QChar(QChar::toTitleCase(ucs)); }
+    inline QChar toCaseFolded() const noexcept { return QChar(QChar::toCaseFolded(ucs)); }
 
     inline Script script() const noexcept { return QChar::script(ucs); }
 
diff --git a/src/corelib/tools/qlocale_p.h b/src/corelib/tools/qlocale_p.h
index 1e3da35a02..37afb8542b 100644
--- a/src/corelib/tools/qlocale_p.h
+++ b/src/corelib/tools/qlocale_p.h
@@ -285,9 +285,9 @@ public:
     quint16 m_language_id, m_script_id, m_country_id;
 
     // FIXME QTBUG-69324: not all unicode code-points map to single-token UTF-16 :-(
-    quint16 m_decimal, m_group, m_list, m_percent, m_zero, m_minus, m_plus, m_exponential;
-    quint16 m_quotation_start, m_quotation_end;
-    quint16 m_alternate_quotation_start, m_alternate_quotation_end;
+    char16_t m_decimal, m_group, m_list, m_percent, m_zero, m_minus, m_plus, m_exponential;
+    char16_t m_quotation_start, m_quotation_end;
+    char16_t m_alternate_quotation_start, m_alternate_quotation_end;
 
     quint16 m_list_pattern_part_start_idx, m_list_pattern_part_start_size;
     quint16 m_list_pattern_part_mid_idx, m_list_pattern_part_mid_size;
@@ -417,7 +417,7 @@ inline char QLocaleData::digitToCLocale(QChar in) const
     if (in == m_group)
         return ',';
 
-    if (in == m_exponential || in == QChar::toUpper(m_exponential))
+    if (in == m_exponential || in == QChar(QChar::toUpper(m_exponential)))
         return 'e';
 
     // In several languages group() is a non-breaking space (U+00A0) or its thin
diff --git a/src/corelib/tools/qregexp.cpp b/src/corelib/tools/qregexp.cpp
index dd38ba0360..d81826b47b 100644
--- a/src/corelib/tools/qregexp.cpp
+++ b/src/corelib/tools/qregexp.cpp
@@ -2035,7 +2035,7 @@ bool QRegExpMatchState::matchHere()
 #ifndef QT_NO_REGEXP_CCLASS
                         const QRegExpCharClass &cc = eng->cl.at(m ^ QRegExpEngine::CharClassBit);
                         if (eng->cs)
-                            inside = cc.in(ch);
+                            inside = cc.in(QChar(ch));
                         else if (cc.negative())
                             inside = cc.in(QChar(ch).toLower()) &&
                                      cc.in(QChar(ch).toUpper());
diff --git a/src/corelib/tools/qstring.cpp b/src/corelib/tools/qstring.cpp
index 47db97cdfc..12506afdef 100644
--- a/src/corelib/tools/qstring.cpp
+++ b/src/corelib/tools/qstring.cpp
@@ -3208,7 +3208,7 @@ QString& QString::replace(QChar ch, const QString &after, Qt::CaseSensitivity cs
         return remove(ch, cs);
 
     if (after.d->size == 1)
-        return replace(ch, after.d->data()[0], cs);
+        return replace(ch, after.front(), cs);
 
     if (d->size == 0)
         return *this;
@@ -6666,7 +6666,7 @@ static QString detachAndConvertCase(T &str, QStringIterator it)
         } else if (Q_UNLIKELY(QChar::requiresSurrogates(uc))) {
             // so far, case convertion never changes planes (guaranteed by the qunicodetables generator)
             pp++;
-            *pp++ = QChar::lowSurrogate(uc + caseDiff);
+            *pp++ = QChar(QChar::lowSurrogate(uc + caseDiff));
         } else {
             *pp++ = QChar(uc + caseDiff);
         }
diff --git a/src/corelib/tools/qstring.h b/src/corelib/tools/qstring.h
index 6788e53057..9896553f7d 100644
--- a/src/corelib/tools/qstring.h
+++ b/src/corelib/tools/qstring.h
@@ -1002,11 +1002,11 @@ inline QString::QString(QLatin1String aLatin1) : d(fromLatin1_helper(aLatin1.lat
 inline int QString::length() const
 { return d->size; }
 inline const QChar QString::at(int i) const
-{ Q_ASSERT(uint(i) < uint(size())); return d->data()[i]; }
+{ Q_ASSERT(uint(i) < uint(size())); return QChar(d->data()[i]); }
 inline const QChar QString::operator[](int i) const
-{ Q_ASSERT(uint(i) < uint(size())); return d->data()[i]; }
+{ Q_ASSERT(uint(i) < uint(size())); return QChar(d->data()[i]); }
 inline const QChar QString::operator[](uint i) const
-{ Q_ASSERT(i < uint(size())); return d->data()[i]; }
+{ Q_ASSERT(i < uint(size())); return QChar(d->data()[i]); }
 inline bool QString::isEmpty() const
 { return d->size == 0; }
 inline const QChar *QString::unicode() const
@@ -1118,11 +1118,11 @@ public:
     {
         using namespace QtPrivate::DeprecatedRefClassBehavior;
         if (Q_LIKELY(i < s.d->size))
-            return s.d->data()[i];
+            return QChar(s.d->data()[i]);
 #ifdef QT_DEBUG
         warn(WarningType::OutOfRange, EmittingClass::QCharRef);
 #endif
-        return 0;
+        return QChar();
     }
     inline QCharRef &operator=(QChar c)
     {
diff --git a/src/platformsupport/input/evdevkeyboard/qevdevkeyboardhandler.cpp b/src/platformsupport/input/evdevkeyboard/qevdevkeyboardhandler.cpp
index bff4a2522c..3555763b89 100644
--- a/src/platformsupport/input/evdevkeyboard/qevdevkeyboardhandler.cpp
+++ b/src/platformsupport/input/evdevkeyboard/qevdevkeyboardhandler.cpp
@@ -231,7 +231,7 @@ void QEvdevKeyboardHandler::processKeyEvent(int nativecode, int unicode, int qtc
 
     QWindowSystemInterface::handleExtendedKeyEvent(0, (isPress ? QEvent::KeyPress : QEvent::KeyRelease),
                                                    qtcode, modifiers, nativecode + 8, 0, int(modifiers),
-                                                   (unicode != 0xffff ) ? QString(unicode) : QString(), autoRepeat);
+                                                   (unicode != 0xffff ) ? QString(QChar(unicode)) : QString(), autoRepeat);
 }
 
 QEvdevKeyboardHandler::KeycodeAction QEvdevKeyboardHandler::processKeycode(quint16 keycode, bool pressed, bool autorepeat)
diff --git a/src/xml/sax/qxml.cpp b/src/xml/sax/qxml.cpp
index 1c45118fb1..1993073cce 100644
--- a/src/xml/sax/qxml.cpp
+++ b/src/xml/sax/qxml.cpp
@@ -1161,12 +1161,12 @@ QChar QXmlInputSource::next()
             d->nextReturnedEndOfData = false;
             fetchData();
             if (d->pos >= d->length) {
-                return EndOfDocument;
+                return QChar(EndOfDocument);
             }
             return next();
         }
         d->nextReturnedEndOfData = true;
-        return EndOfData;
+        return QChar(EndOfData);
     }
 
     // QXmlInputSource has no way to signal encoding errors. The best we can do
@@ -1174,7 +1174,7 @@ QChar QXmlInputSource::next()
     // will then just call this function again to get the next char.
     QChar c = d->unicode[d->pos++];
     if (c.unicode() == EndOfData)
-        c = EndOfDocument;
+        c = QChar(EndOfDocument);
     return c;
 }
 
@@ -1313,8 +1313,8 @@ static QString extractEncodingDecl(const QString &text, bool *needMoreText)
         return QString();
 
     while (pos < endPos) {
-        ushort uc = text.at(pos).unicode();
-        if (uc == '\'' || uc == '"')
+        QChar uc = text.at(pos);
+        if (uc == u'\'' || uc == u'"')
             break;
         ++pos;
     }
@@ -1325,8 +1325,8 @@ static QString extractEncodingDecl(const QString &text, bool *needMoreText)
     QString encoding;
     ++pos;
     while (pos < endPos) {
-        ushort uc = text.at(pos).unicode();
-        if (uc == '\'' || uc == '"')
+        QChar uc = text.at(pos);
+        if (uc == u'\'' || uc == u'"')
             break;
         encoding.append(uc);
         ++pos;
@@ -7800,7 +7800,7 @@ void QXmlSimpleReaderPrivate::next()
     c = inputSource->next();
     // If we are not incremental parsing, we just skip over EndOfData chars to give the
     // parser an uninterrupted stream of document chars.
-    if (c == QXmlInputSource::EndOfData && parseStack == nullptr)
+    if (c == QChar(QXmlInputSource::EndOfData) && parseStack == nullptr)
         c = inputSource->next();
     if (uc == '\n') {
         lineNr++;
@@ -7877,7 +7877,7 @@ void QXmlSimpleReaderPrivate::init(const QXmlInputSource *i)
 */
 void QXmlSimpleReaderPrivate::initData()
 {
-    c = QXmlInputSource::EndOfData;
+    c = QChar(QXmlInputSource::EndOfData);
     xmlRefStack.clear();
     next();
 }
@@ -7925,7 +7925,7 @@ void QXmlSimpleReaderPrivate::unexpectedEof(ParseFunction where, int state)
     if (parseStack == nullptr) {
         reportParseError(QLatin1String(XMLERR_UNEXPECTEDEOF));
     } else {
-        if (c == QXmlInputSource::EndOfDocument) {
+        if (c == QChar(QXmlInputSource::EndOfDocument)) {
             reportParseError(QLatin1String(XMLERR_UNEXPECTEDEOF));
         } else {
             pushParseState(where, state);