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, 8 insertions, 8 deletions

diff --git a/tests/auto/corelib/tools/collections/tst_collections.cpp b/tests/auto/corelib/tools/collections/tst_collections.cpp
index 85c6f7e6e1..50f9f155d0 100644
--- a/tests/auto/corelib/tools/collections/tst_collections.cpp
+++ b/tests/auto/corelib/tools/collections/tst_collections.cpp
@@ -1121,17 +1121,17 @@ void tst_Collections::hash()
         Hash hash;
         QString key = QLatin1String("  ");
         for (int i = 0; i < 10; ++i) {
-            key[0] = i + '0';
+            key[0] = QChar(i + '0');
             for (int j = 0; j < 10; ++j) {
-                key[1] = j + '0';
+                key[1] = QChar(j + '0');
                 hash.insert(key, "V" + key);
             }
         }
 
         for (int i = 0; i < 10; ++i) {
-            key[0] = i + '0';
+            key[0] = QChar(i + '0');
             for (int j = 0; j < 10; ++j) {
-                key[1] = j + '0';
+                key[1] = QChar(j + '0');
                 hash.remove(key);
             }
         }
diff --git a/tests/auto/corelib/tools/qhash/tst_qhash.cpp b/tests/auto/corelib/tools/qhash/tst_qhash.cpp
index 359095c3d0..f61dfda720 100644
--- a/tests/auto/corelib/tools/qhash/tst_qhash.cpp
+++ b/tests/auto/corelib/tools/qhash/tst_qhash.cpp
@@ -309,17 +309,17 @@ void tst_QHash::insert1()
         Hash hash;
         QString key = QLatin1String("  ");
         for (int i = 0; i < 10; ++i) {
-            key[0] = i + '0';
+            key[0] = QChar(i + '0');
             for (int j = 0; j < 10; ++j) {
-                key[1] = j + '0';
+                key[1] = QChar(j + '0');
                 hash.insert(key, "V" + key);
             }
         }
 
         for (int i = 0; i < 10; ++i) {
-            key[0] = i + '0';
+            key[0] = QChar(i + '0');
             for (int j = 0; j < 10; ++j) {
-                key[1] = j + '0';
+                key[1] = QChar(j + '0');
                 hash.remove(key);
             }
         }