ClangCodeModel: Work around clangd cursor issue

If the cursor is right before the "." in a member access expression,
clangd interprets it as belonging to the member instead of the base
expression, which leads to unexpected behavior.
Work around this by sending a cursor position one to the left of the
real one to clangd in such cases.

Change-Id: I429ee9189760ccb02d231acfcb94ab6cfde3cd8d
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/languageclient/client.cpp

@@ -523,8 +523,10 @@ void Client::requestDocumentHighlights(TextEditor::TextEditorWidget *widget)
     if (m_highlightRequests.contains(widget))
         cancelRequest(m_highlightRequests.take(widget));
 
+    const QTextCursor adjustedCursor = adjustedCursorForHighlighting(widget->textCursor(),
+                                                                     widget->textDocument());
     DocumentHighlightsRequest request(
-        TextDocumentPositionParams(TextDocumentIdentifier(uri), Position(widget->textCursor())));
+        TextDocumentPositionParams(TextDocumentIdentifier(uri), Position{adjustedCursor}));
     auto connection = connect(widget, &QObject::destroyed, this, [this, widget]() {
         if (m_highlightRequests.contains(widget))
             cancelRequest(m_highlightRequests.take(widget));
@@ -1570,4 +1572,11 @@ bool Client::sendWorkspceFolderChanges() const
     return false;
 }
 
+QTextCursor Client::adjustedCursorForHighlighting(const QTextCursor &cursor,
+                                                  TextEditor::TextDocument *doc)
+{
+    Q_UNUSED(doc)
+    return cursor;
+}
+
 } // namespace LanguageClient