ClangFormat: Fix removal of common prefix and suffix

Amends 61fc1fd452.

Fixes: QTCREATORBUG-31004
Change-Id: I9fea637d36a97b472204a7601efcec9e0f610eb7
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangformat/clangformatbaseindenter.cpp

@@ -433,8 +433,10 @@ static ChangeSet convertReplacements(const QTextDocument *doc,
         QString replacementText = QString::fromStdString(replacement.getReplacementText().str());
         replacementText.replace("\r", "");
         auto sameCharAt = [&](int replacementOffset) {
-            if (replacementText.size() <= replacementOffset || replacementOffset < 0)
+            if (utf16Length == 0 || replacementText.size() <= replacementOffset
+                || replacementOffset < 0) {
                 return false;
+            }
             const QChar docChar = doc->characterAt(utf16Offset + replacementOffset);
             const QChar replacementChar = replacementText.at(replacementOffset);
             return docChar == replacementChar
@@ -444,7 +446,7 @@ static ChangeSet convertReplacements(const QTextDocument *doc,
         while (sameCharAt(0)) {
             ++utf16Offset;
             --utf16Length;
-            replacementText = replacementText.mid(1);
+            replacementText.removeFirst();
         }
         // remove identical suffix from replacement text
         while (sameCharAt(utf16Length - 1)) {

src/plugins/clangformat/tests/clangformat-test.cpp

@@ -118,6 +118,7 @@ private slots:
     void testIndentationInTheBegginingOfLine();
     void testIndentationReturnAfterIf();
     void testIndentationReturnAfterIfSomthingFunction();
+    void testReformatQualifier();
 
 private:
     void insertLines(const std::vector<QString> &lines);
@@ -999,6 +1000,25 @@ void ClangFormatTest::testIndentationReturnAfterIfSomthingFunction()
                                    "}"}));
 }
 
+void ClangFormatTest::testReformatQualifier()
+{
+    insertLines({
+        "struct S",
+        "{",
+        "    S &operator=(S const &s);",
+        "};",
+        "S &S::operator=(const S &s) {}"
+    });
+    m_extendedIndenter->autoIndent(*m_cursor, TextEditor::TabSettings());
+    const std::vector<QString> expected{
+        "struct S",
+        "{",
+        "    S &operator=(S const &s);",
+        "};",
+        "S &S::operator=(S const &s) {}"};
+    QCOMPARE(documentLines(), expected);
+}
+
 QObject *createClangFormatTest()
 {
     return new ClangFormatTest;

src/plugins/clangformat/tests/data/.clang-format

@@ -96,6 +96,7 @@ PenaltyBreakString: 600
 PenaltyExcessCharacter: 50
 PenaltyReturnTypeOnItsOwnLine: 300
 PointerAlignment: Right
+QualifierAlignment: Right
 ReflowComments:  false
 SortIncludes:    true
 SortUsingDeclarations: true