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, 1 insertions, 1 deletions

diff --git a/tests/benchmarks/widgets/itemviews/qheaderview/qheaderviewbench.cpp b/tests/benchmarks/widgets/itemviews/qheaderview/qheaderviewbench.cpp
index 49ce060580..65d467d345 100644
--- a/tests/benchmarks/widgets/itemviews/qheaderview/qheaderviewbench.cpp
+++ b/tests/benchmarks/widgets/itemviews/qheaderview/qheaderviewbench.cpp
@@ -126,7 +126,7 @@ void BenchQHeaderView::init()
         m_model->setData(m_model->index(i, 0), QVariant(i));
         s.setNum(i);
         s += QLatin1Char('.');
-        s += 'a' + (i % 25);
+        s += QLatin1Char('a' + (i % 25));
         m_model->setData(m_model->index(i, 1), QVariant(s));
     }
     m_tv->setUpdatesEnabled(m_updatesEnabled);