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, 6 insertions, 6 deletions

diff --git a/tests/auto/corelib/io/qfile/tst_qfile.cpp b/tests/auto/corelib/io/qfile/tst_qfile.cpp
index e5b7051997..e408cd3e48 100644
--- a/tests/auto/corelib/io/qfile/tst_qfile.cpp
+++ b/tests/auto/corelib/io/qfile/tst_qfile.cpp
@@ -3182,7 +3182,7 @@ void tst_QFile::mapResource()
     QCOMPARE(file.error(), error);
     QVERIFY((error == QFile::NoError) ? (memory != 0) : (memory == 0));
     if (error == QFile::NoError)
-        QCOMPARE(QString(memory[0]), QString::number(offset + 1));
+        QCOMPARE(QString(QChar(memory[0])), QString::number(offset + 1));
     QVERIFY(file.unmap(memory));
 }
 
diff --git a/tests/auto/corelib/io/qurlinternal/tst_qurlinternal.cpp b/tests/auto/corelib/io/qurlinternal/tst_qurlinternal.cpp
index da9477ca84..4b77820028 100644
--- a/tests/auto/corelib/io/qurlinternal/tst_qurlinternal.cpp
+++ b/tests/auto/corelib/io/qurlinternal/tst_qurlinternal.cpp
@@ -517,23 +517,23 @@ void tst_QUrlInternal::nameprep_highcodes_data()
     QTest::addColumn<int>("rc");
 
     {
-        QChar st[] = { '-', 0xd801, 0xdc1d, 'a' };
-        QChar se[] = { '-', 0xd801, 0xdc45, 'a' };
+        QChar st[] = { '-', QChar(0xd801), QChar(0xdc1d), 'a' };
+        QChar se[] = { '-', QChar(0xd801), QChar(0xdc45), 'a' };
         QTest::newRow("highcodes (U+1041D)")
             << QString(st, sizeof(st)/sizeof(st[0]))
             << QString(se, sizeof(se)/sizeof(se[0]))
             << QString() << 0 << 0;
     }
     {
-        QChar st[] = { 0x011C, 0xd835, 0xdf6e, 0x0110 };
-        QChar se[] = { 0x011D, 0x03C9, 0x0111 };
+        QChar st[] = { QChar(0x011C), QChar(0xd835), QChar(0xdf6e), QChar(0x0110) };
+        QChar se[] = { QChar(0x011D), QChar(0x03C9), QChar(0x0111) };
         QTest::newRow("highcodes (U+1D76E)")
             << QString(st, sizeof(st)/sizeof(st[0]))
             << QString(se, sizeof(se)/sizeof(se[0]))
             << QString() << 0 << 0;
     }
     {
-        QChar st[] = { 'D', 'o', '\'', 0x2060, 'h' };
+        QChar st[] = { 'D', 'o', '\'', QChar(0x2060), 'h' };
         QChar se[] = { 'd', 'o', '\'', 'h' };
         QTest::newRow("highcodes (D, o, ', U+2060, h)")
             << QString(st, sizeof(st)/sizeof(st[0]))