CppEditor: Adapt function declaration

... when changing the name of a function parameter from a point of use,
rather than from the definition.
The normal function decl/def link mechanism only covers editing in the
signature.

Task-number: QTCREATORBUG-29925
Change-Id: I34ff90117685184b9fc72937b401976274f4876c
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/plugins/cppeditor/cppfunctionparamrenaminghandler.cpp

@@ -0,0 +1,112 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
+
+#include "cppfunctionparamrenaminghandler.h"
+
+#include "cppeditorwidget.h"
+#include "cpplocalrenaming.h"
+#include "cppfunctiondecldeflink.h"
+
+#include <cplusplus/AST.h>
+#include <cplusplus/ASTPath.h>
+#include <texteditor/textdocument.h>
+
+#include <memory>
+
+using namespace CPlusPlus;
+
+namespace CppEditor::Internal {
+
+using DeclDefLinkPtr = QSharedPointer<FunctionDeclDefLink>;
+
+class CppFunctionParamRenamingHandler::Private
+{
+public:
+    Private(CppEditorWidget &editorWidget, CppLocalRenaming &localRenaming);
+
+    void handleRenamingStarted();
+    void handleRenamingFinished();
+    void handleLinkFound(const DeclDefLinkPtr &link);
+    void findLink(FunctionDefinitionAST &func, const SemanticInfo &semanticInfo);
+
+    CppEditorWidget &editorWidget;
+    CppLocalRenaming &localRenaming;
+    std::unique_ptr<FunctionDeclDefLinkFinder> linkFinder;
+    DeclDefLinkPtr link;
+};
+
+CppFunctionParamRenamingHandler::CppFunctionParamRenamingHandler(
+    CppEditorWidget &editorWidget, CppLocalRenaming &localRenaming)
+    : d(new Private(editorWidget, localRenaming)) {}
+
+CppFunctionParamRenamingHandler::~CppFunctionParamRenamingHandler() { delete d; }
+
+CppFunctionParamRenamingHandler::Private::Private(
+    CppEditorWidget &editorWidget, CppLocalRenaming &localRenaming)
+    : editorWidget(editorWidget), localRenaming(localRenaming)
+{
+    QObject::connect(&localRenaming, &CppLocalRenaming::started,
+                     &editorWidget, [this] { handleRenamingStarted(); });
+    QObject::connect(&localRenaming, &CppLocalRenaming::finished,
+                     &editorWidget, [this] { handleRenamingFinished(); });
+}
+
+void CppFunctionParamRenamingHandler::Private::handleRenamingStarted()
+{
+    linkFinder.reset();
+    link.clear();
+
+    // Are we currently on the function signature? In this case, the normal decl/def link
+    // mechanism kicks in and we don't have to do anything.
+    if (editorWidget.declDefLink())
+        return;
+
+    // If we find a surrounding function definition, start up the decl/def link finder.
+    const SemanticInfo semanticInfo = editorWidget.semanticInfo();
+    if (!semanticInfo.doc || !semanticInfo.doc->translationUnit())
+        return;
+    const QList<AST *> astPath = ASTPath(semanticInfo.doc)(editorWidget.textCursor());
+    for (auto it = astPath.rbegin(); it != astPath.rend(); ++it) {
+        if (const auto func = (*it)->asFunctionDefinition()) {
+            findLink(*func, semanticInfo);
+            return;
+        }
+    }
+}
+
+void CppFunctionParamRenamingHandler::Private::handleRenamingFinished()
+{
+    if (link) {
+        link->apply(&editorWidget, false);
+        link.clear();
+    }
+}
+
+void CppFunctionParamRenamingHandler::Private::handleLinkFound(const DeclDefLinkPtr &link)
+{
+    if (localRenaming.isActive())
+        this->link = link;
+    linkFinder.reset();
+}
+
+void CppFunctionParamRenamingHandler::Private::findLink(FunctionDefinitionAST &func,
+                                                        const SemanticInfo &semanticInfo)
+{
+    if (!func.declarator)
+        return;
+
+    // The finder needs a cursor that points to the signature, so provide one.
+    QTextDocument * const doc = editorWidget.textDocument()->document();
+    const int pos = semanticInfo.doc->translationUnit()->getTokenEndPositionInDocument(
+        func.declarator->firstToken(), doc);
+    QTextCursor cursor(doc);
+    cursor.setPosition(pos);
+    linkFinder.reset(new FunctionDeclDefLinkFinder);
+    QObject::connect(linkFinder.get(), &FunctionDeclDefLinkFinder::foundLink,
+            &editorWidget, [this](const DeclDefLinkPtr &link) {
+        handleLinkFound(link);
+    });
+    linkFinder->startFindLinkAt(cursor, semanticInfo.doc, semanticInfo.snapshot);
+}
+
+} // namespace CppEditor::Internal