tst_QAnyStringView: add fromX for various char-like types

These were not covered by the existing tests.

Pick-to: 6.5 6.2
Change-Id: I909ea3aa5b676904dc72ecf8ce32b73cca1b6af7
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
(cherry picked from commit 39189190fee872d2e6fcaca0f5c10d0ba6a70ea6)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

tests/auto/corelib/text/qanystringview/tst_qanystringview.cpp

@@ -355,6 +355,29 @@ private Q_SLOTS:
         fromLiteral(u8"Hello, World!"); // char[] in <= C++17, char8_t[] in >= C++20
     }
 
+    void fromChar() const { fromCharacter('\xE4', 1); }
+    void fromUChar() const { fromCharacter(static_cast<unsigned char>('\xE4'), 1); }
+    void fromSChar() const { fromCharacter(static_cast<signed char>('\xE4'), 1); }
+    void fromChar16T() const { fromCharacter(u'ä', 1); }
+    void fromUShort() const { fromCharacter(ushort(0xE4), 1); }
+    void fromChar32T() const {
+        fromCharacter(U'ä', 1);
+        if (QTest::currentTestFailed())
+            return;
+        fromCharacter(U'\x1F0A0', 2); // U+1F0A0: PLAYING CARD BACK
+    }
+    void fromWCharT() const {
+        ONLY_WIN(fromCharacter(L'ä', 1)); // should work on Unix, too (char32_t does)
+    }
+    void fromQChar() const { fromCharacter(QChar(u'ä'), 1); }
+    void fromQLatin1Char() const { fromCharacter(QLatin1Char('\xE4'), 1); }
+    void fromQCharSpecialCharacter() const {
+        fromCharacter(QChar::ReplacementCharacter, 1);
+        if (QTest::currentTestFailed())
+            return;
+        fromCharacter(QChar::LastValidCodePoint, 1);
+    }
+
     void fromChar16TStar() const { fromLiteral(u"Hello, World!"); }
     void fromWCharTStar() const { ONLY_WIN(fromLiteral(L"Hello, World!")); }
 
@@ -391,6 +414,8 @@ private:
     template <typename Char>
     void fromLiteral(const Char *arg) const;
     template <typename Char>
+    void fromCharacter(Char arg, qsizetype expectedSize) const;
+    template <typename Char>
     void fromRange() const;
     template <typename Char, typename Container>
     void fromContainer() const;
@@ -671,6 +696,40 @@ void tst_QAnyStringView::fromLiteral(const Char *arg) const
     conversion_tests(arg);
 }
 
+template<typename Char>
+void tst_QAnyStringView::fromCharacter(Char arg, qsizetype expectedSize) const
+{
+    // Need to re-create a new QASV(arg) each time, QASV(Char).data() dangles
+    // after the end of the Full Expression:
+
+    QCOMPARE(QAnyStringView(arg).size(), expectedSize);
+
+    // QCOMPARE(QAnyStringView(arg), arg); // not all pairs compile, so do it manually:
+
+    const QChar chars[] = {
+        QAnyStringView(arg).front(),
+        QAnyStringView(arg).back(),
+    };
+
+    switch (expectedSize) {
+    case 1:
+        if constexpr (std::is_same_v<Char, signed char>) // QChar doesn't have a ctor for this
+            QCOMPARE(chars[0], QChar(uchar(arg)));
+        else
+            QCOMPARE(chars[0], QChar(arg));
+        break;
+    case 2:
+        QCOMPARE_EQ(QAnyStringView(arg), QStringView::fromArray(chars));
+        if constexpr (std::is_convertible_v<Char, char32_t>)
+            QCOMPARE_EQ(QAnyStringView(arg), QStringView(QChar::fromUcs4(arg)));
+        break;
+    default:
+        QFAIL("Don't know how to compare this type to QAnyStringView");
+    }
+
+    // conversion_tests() would produce dangling references
+}
+
 template <typename Char>
 void tst_QAnyStringView::fromRange() const
 {