ClangCodeModel: Support access type categorization

... with "Find Usages", as we do in the built-in code model.
Note 1: This is very slow, so it's for now only enabled if the
        search results come from a small number of files.
        Possible ways of speeding up the operation
        to be investigated.
Note 2: All test cases from the old code model also pass here,
        but checking with non-trivial real-world projects
        shows a lot of mis-categorizations.
        Well will fix them one by one.
Note 3: This functionality requires clangd >= 13.

Change-Id: Ib3500b52996dbbf9d7d9712d729179bcbd3262fc
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/CMakeLists.txt

@@ -1,7 +1,7 @@
 add_qtc_plugin(ClangCodeModel
   CONDITION TARGET libclang
   DEPENDS ClangSupport CPlusPlus
-  PLUGIN_DEPENDS Core CppTools LanguageClient TextEditor
+  PLUGIN_DEPENDS Core CppTools LanguageClient QtSupport TextEditor
   PLUGIN_TEST_DEPENDS CppEditor QmakeProjectManager
   SOURCES
     clangactivationsequencecontextprocessor.cpp clangactivationsequencecontextprocessor.h
@@ -52,5 +52,6 @@ extend_qtc_plugin(ClangCodeModel
     test/clangautomationutils.cpp test/clangautomationutils.h
     test/clangbatchfileprocessor.cpp test/clangbatchfileprocessor.h
     test/clangcodecompletion_test.cpp test/clangcodecompletion_test.h
+    test/clangdtests.cpp test/clangdtests.h
     test/data/clangtestdata.qrc
 )

src/plugins/clangcodemodel/clangcodemodel.pro

@@ -96,11 +96,13 @@ equals(TEST, 1) {
         test/clangautomationutils.h \
         test/clangbatchfileprocessor.h \
         test/clangcodecompletion_test.h \
+        test/clangdtests.h
 
     SOURCES += \
         test/clangautomationutils.cpp \
         test/clangbatchfileprocessor.cpp \
         test/clangcodecompletion_test.cpp \
+        test/clangdtests.cpp
 
     RESOURCES += test/data/clangtestdata.qrc
     OTHER_FILES += $$files(test/data/*)

src/plugins/clangcodemodel/clangcodemodel.qbs

@@ -8,6 +8,7 @@ QtcPlugin {
     Depends { name: "Core" }
     Depends { name: "CppTools" }
     Depends { name: "ProjectExplorer" }
+    Depends { name: "QtSupport"; condition: qtc.testsEnabled }
     Depends { name: "TextEditor" }
     Depends { name: "Utils" }
     Depends { name: "ClangSupport" }
@@ -114,6 +115,8 @@ QtcPlugin {
             "clangbatchfileprocessor.h",
             "clangcodecompletion_test.cpp",
             "clangcodecompletion_test.h",
+            "clangdtests.cpp",
+            "clangdtests.h",
             "data/clangtestdata.qrc",
         ]
     }

src/plugins/clangcodemodel/clangcodemodel_dependencies.pri

@@ -10,3 +10,5 @@ QTC_PLUGIN_DEPENDS += \
 QTC_TEST_DEPENDS += \
     cppeditor \
     qmakeprojectmanager
+
+equals(TEST, 1): QTC_PLUGIN_DEPENDS += qtsupport

src/plugins/clangcodemodel/clangcodemodelplugin.cpp

@@ -32,6 +32,7 @@
 #ifdef WITH_TESTS
 #  include "test/clangbatchfileprocessor.h"
 #  include "test/clangcodecompletion_test.h"
+#  include "test/clangdtests.h"
 #endif
 
 #include <coreplugin/actionmanager/actioncontainer.h>
@@ -204,6 +205,7 @@ QVector<QObject *> ClangCodeModelPlugin::createTestObjects() const
 {
     return {
         new Tests::ClangCodeCompletionTest,
+        new Tests::ClangdTests,
     };
 }
 #endif

src/plugins/clangcodemodel/clangdclient.cpp

@@ -25,10 +25,21 @@
 
 #include "clangdclient.h"
 
+#include <coreplugin/find/searchresultitem.h>
+#include <coreplugin/find/searchresultwindow.h>
+#include <cplusplus/FindUsages.h>
 #include <cpptools/cppcodemodelsettings.h>
+#include <cpptools/cppfindreferences.h>
 #include <cpptools/cpptoolsreuse.h>
 #include <languageclient/languageclientinterface.h>
 
+#include <QFile>
+#include <QHash>
+#include <QPointer>
+#include <QRegularExpression>
+
+using namespace CPlusPlus;
+using namespace Core;
 using namespace LanguageClient;
 using namespace LanguageServerProtocol;
 
@@ -36,13 +47,240 @@ namespace ClangCodeModel {
 namespace Internal {
 
 static Q_LOGGING_CATEGORY(clangdLog, "qtc.clangcodemodel.clangd", QtWarningMsg);
-
 static QString indexingToken() { return "backgroundIndexProgress"; }
 
+class AstParams : public JsonObject
+{
+public:
+    AstParams() {}
+    AstParams(const TextDocumentIdentifier &document, const Range &range);
+    using JsonObject::JsonObject;
+
+    // The open file to inspect.
+    TextDocumentIdentifier textDocument() const
+    { return typedValue<TextDocumentIdentifier>(textDocumentKey); }
+    void setTextDocument(const TextDocumentIdentifier &id) { insert(textDocumentKey, id); }
+
+    // The region of the source code whose AST is fetched. The highest-level node that entirely
+    // contains the range is returned.
+    Utils::optional<Range> range() const { return optionalValue<Range>(rangeKey); }
+    void setRange(const Range &range) { insert(rangeKey, range); }
+
+    bool isValid() const override { return contains(textDocumentKey); }
+};
+
+class AstNode : public JsonObject
+{
+public:
+    using JsonObject::JsonObject;
+
+    static constexpr char roleKey[] = "role";
+    static constexpr char arcanaKey[] = "arcana";
+
+    // The general kind of node, such as “expression”. Corresponds to clang’s base AST node type,
+    // such as Expr. The most common are “expression”, “statement”, “type” and “declaration”.
+    QString role() const { return typedValue<QString>(roleKey); }
+
+    // The specific kind of node, such as “BinaryOperator”. Corresponds to clang’s concrete
+    // node class, with Expr etc suffix dropped.
+    QString kind() const { return typedValue<QString>(kindKey); }
+
+    // Brief additional details, such as ‘||’. Information present here depends on the node kind.
+    Utils::optional<QString> detail() const { return optionalValue<QString>(detailKey); }
+
+    // One line dump of information, similar to that printed by clang -Xclang -ast-dump.
+    // Only available for certain types of nodes.
+    Utils::optional<QString> arcana() const { return optionalValue<QString>(arcanaKey); }
+
+    // The part of the code that produced this node. Missing for implicit nodes, nodes produced
+    // by macro expansion, etc.
+    Range range() const { return typedValue<Range>(rangeKey); }
+
+    // Descendants describing the internal structure. The tree of nodes is similar to that printed
+    // by clang -Xclang -ast-dump, or that traversed by clang::RecursiveASTVisitor.
+    Utils::optional<QList<AstNode>> children() const { return optionalArray<AstNode>(childrenKey); }
+
+    bool hasRange() const { return contains(rangeKey); }
+
+    bool arcanaContains(const QString &s) const
+    {
+        const Utils::optional<QString> arcanaString = arcana();
+        return arcanaString && arcanaString->contains(s);
+    }
+
+    bool detailIs(const QString &s) const
+    {
+        return detail() && detail().value() == s;
+    }
+
+    QString type() const
+    {
+        const Utils::optional<QString> arcanaString = arcana();
+        if (!arcanaString)
+            return {};
+        const int quote1Offset = arcanaString->indexOf('\'');
+        if (quote1Offset == -1)
+            return {};
+        const int quote2Offset = arcanaString->indexOf('\'', quote1Offset + 1);
+        if (quote2Offset == -1)
+            return {};
+        return arcanaString->mid(quote1Offset + 1, quote2Offset - quote1Offset - 1);
+    }
+
+    // Returns true <=> the type is "recursively const".
+    // E.g. returns true for "const int &", "const int *" and "const int * const *",
+    // and false for "int &" and "const int **".
+    // For non-pointer types such as "int", we check whether they are uses as lvalues
+    // or rvalues.
+    bool hasConstType() const
+    {
+        QString theType = type();
+        if (theType.endsWith("const"))
+            theType.chop(5);
+        const int ptrRefCount = theType.count('*') + theType.count('&');
+        const int constCount = theType.count("const");
+        if (ptrRefCount == 0)
+            return constCount > 0 || detailIs("LValueToRValue");
+        return ptrRefCount <= constCount;
+    }
+
+    bool childContainsRange(int index, const Range &range) const
+    {
+        const Utils::optional<QList<AstNode>> childList = children();
+        return childList && childList->size() > index
+                && childList->at(index).range().contains(range);
+    }
+
+    QString operatorString() const
+    {
+        if (kind() == "BinaryOperator")
+            return detail().value_or(QString());
+        QTC_ASSERT(kind() == "CXXOperatorCall", return {});
+        const Utils::optional<QString> arcanaString = arcana();
+        if (!arcanaString)
+            return {};
+        const int closingQuoteOffset = arcanaString->lastIndexOf('\'');
+        if (closingQuoteOffset <= 0)
+            return {};
+        const int openingQuoteOffset = arcanaString->lastIndexOf('\'', closingQuoteOffset - 1);
+        if (openingQuoteOffset == -1)
+            return {};
+        return arcanaString->mid(openingQuoteOffset + 1, closingQuoteOffset
+                                 - openingQuoteOffset - 1);
+    }
+
+    bool isValid() const override
+    {
+        return contains(roleKey) && contains(kindKey);
+    }
+};
+
+static QList<AstNode> getAstPath(const AstNode &root, const Range &range)
+{
+    QList<AstNode> path;
+    QList<AstNode> queue{root};
+    bool isRoot = true;
+    while (!queue.isEmpty()) {
+        AstNode curNode = queue.takeFirst();
+        if (!isRoot && !curNode.hasRange())
+            continue;
+        if (curNode.range() == range)
+            return path << curNode;
+        if (isRoot || curNode.range().contains(range)) {
+            path << curNode;
+            const auto children = curNode.children();
+            if (!children)
+                break;
+            queue = children.value();
+        }
+        isRoot = false;
+    }
+    return path;
+}
+
+static Usage::Type getUsageType(const QList<AstNode> &path)
+{
+    bool potentialWrite = false;
+    const bool symbolIsDataType = path.last().role() == "type" && path.last().kind() == "Record";
+    for (auto pathIt = path.rbegin(); pathIt != path.rend(); ++pathIt) {
+        if (pathIt->arcanaContains("non_odr_use_unevaluated"))
+            return Usage::Type::Other;
+        if (pathIt->kind() == "CXXDelete")
+            return Usage::Type::Write;
+        if (pathIt->kind() == "CXXNew")
+            return Usage::Type::Other;
+        if (pathIt->kind() == "Switch" || pathIt->kind() == "If")
+            return Usage::Type::Read;
+        if (pathIt->kind() == "Call" || pathIt->kind() == "CXXMemberCall")
+            return potentialWrite ? Usage::Type::WritableRef : Usage::Type::Read;
+        if ((pathIt->kind() == "DeclRef" || pathIt->kind() == "Member")
+                && pathIt->arcanaContains("lvalue")) {
+            potentialWrite = true;
+        }
+        if (pathIt->role() == "declaration") {
+            if (symbolIsDataType)
+                return Usage::Type::Other;
+            if (pathIt->arcanaContains("cinit")) {
+                if (pathIt == path.rbegin())
+                    return Usage::Type::Initialization;
+                if (pathIt->childContainsRange(0, path.last().range()))
+                    return Usage::Type::Initialization;
+                if (!pathIt->hasConstType())
+                    return Usage::Type::WritableRef;
+                return Usage::Type::Read;
+            }
+            return Usage::Type::Declaration;
+        }
+        if (pathIt->kind() == "MemberInitializer")
+            return pathIt == path.rbegin() ? Usage::Type::Write : Usage::Type::Read;
+        if (pathIt->kind() == "UnaryOperator"
+                && (pathIt->detailIs("++") || pathIt->detailIs("--"))) {
+            return Usage::Type::Write;
+        }
+
+        // LLVM uses BinaryOperator only for built-in types; for classes, CXXOperatorCall
+        // is used. The latter has an additional node at index 0, so the left-hand side
+        // of an assignment is at index 1.
+        const bool isBinaryOp = pathIt->kind() == "BinaryOperator";
+        const bool isOpCall = pathIt->kind() == "CXXOperatorCall";
+        if (isBinaryOp || isOpCall) {
+            if (isOpCall && symbolIsDataType) // Constructor invocation.
+                return Usage::Type::Other;
+
+            const QString op = pathIt->operatorString();
+            if (op.endsWith("=") && op != "==") { // Assignment.
+                const int lhsIndex = isBinaryOp ? 0 : 1;
+                if (pathIt->childContainsRange(lhsIndex, path.last().range()))
+                    return Usage::Type::Write;
+                return potentialWrite ? Usage::Type::WritableRef : Usage::Type::Read;
+            }
+            return Usage::Type::Read;
+        }
+
+        if (pathIt->kind() == "ImplicitCast") {
+            if (pathIt->detailIs("FunctionToPointerDecay"))
+                return Usage::Type::Other;
+            if (pathIt->hasConstType())
+                return Usage::Type::Read;
+            potentialWrite = true;
+            continue;
+        }
+    }
+
+    return Usage::Type::Other;
+}
+
+class AstRequest : public Request<AstNode, std::nullptr_t, AstParams>
+{
+public:
+    using Request::Request;
+    explicit AstRequest(const AstParams &params) : Request("textDocument/ast", params) {}
+};
+
 static BaseClientInterface *clientInterface(const Utils::FilePath &jsonDbDir)
 {
     Utils::CommandLine cmd{CppTools::codeModelSettings()->clangdFilePath(),
-                           {"--index", "--background-index", "--limit-results=0"}};
+                           {"--background-index", "--limit-results=0"}};
     if (!jsonDbDir.isEmpty())
         cmd.addArg("--compile-commands-dir=" + jsonDbDir.toString());
     if (clangdLog().isDebugEnabled())
@@ -52,8 +290,44 @@ static BaseClientInterface *clientInterface(const Utils::FilePath &jsonDbDir)
     return interface;
 }
 
+class ReferencesFileData {
+public:
+    QList<QPair<Range, QString>> rangesAndLineText;
+    QString fileContent;
+    AstNode ast;
+};
+class ReferencesData {
+public:
+    void setCanceled() { search->setUserData(true); }
+    bool isCanceled() const { return search && search->userData().toBool(); }
+
+    QMap<DocumentUri, ReferencesFileData> fileData;
+    QList<MessageId> pendingAstRequests;
+    QPointer<SearchResult> search;
+    quint64 key;
+};
+
+class ClangdClient::Private
+{
+public:
+    Private(ClangdClient *q) : q(q) {}
+
+    void handleFindUsagesResult(quint64 key, const QList<Location> &locations);
+    void addSearchResultsForFile(const ReferencesData &refData, const Utils::FilePath &file,
+                                 const ReferencesFileData &fileData);
+    void reportAllSearchResultsAndFinish(const ReferencesData &data);
+    void finishSearch(const ReferencesData &refData, bool canceled);
+
+    ClangdClient * const q;
+    QHash<quint64, ReferencesData> runningFindUsages;
+    Utils::optional<QVersionNumber> versionNumber;
+    quint64 nextFindUsagesKey = 0;
+    bool isFullyIndexed = false;
+    bool isTesting = false;
+};
+
 ClangdClient::ClangdClient(ProjectExplorer::Project *project, const Utils::FilePath &jsonDbDir)
-    : Client(clientInterface(jsonDbDir))
+    : Client(clientInterface(jsonDbDir)), d(new Private(this))
 {
     setName(tr("clangd"));
     LanguageFilter langFilter;
@@ -69,11 +343,252 @@ ClangdClient::ClangdClient(ProjectExplorer::Project *project, const Utils::FileP
     setCurrentProject(project);
     connect(this, &Client::workDone, this, [this](const ProgressToken &token) {
         const QString * const val = Utils::get_if<QString>(&token);
-        if (val && *val == indexingToken())
+        if (val && *val == indexingToken()) {
-            m_isFullyIndexed = true;
+            d->isFullyIndexed = true;
+            emit indexingFinished();
+        }
     });
+
+    connect(this, &Client::initialized, this, [this] {
+        // If we get this signal while there are pending searches, it means that
+        // the client was re-initialized, i.e. clangd crashed.
+
+        // Report all search results found so far.
+        for (quint64 key : d->runningFindUsages.keys())
+            d->reportAllSearchResultsAndFinish(d->runningFindUsages.value(key));
+        QTC_CHECK(d->runningFindUsages.isEmpty());
+    });
+
     start();
 }
 
+ClangdClient::~ClangdClient()
+{
+    delete d;
+}
+
+bool ClangdClient::isFullyIndexed() const { return d->isFullyIndexed; }
+
+void ClangdClient::openExtraFile(const Utils::FilePath &filePath, const QString &content)
+{
+    QFile cxxFile(filePath.toString());
+    if (content.isEmpty() && !cxxFile.open(QIODevice::ReadOnly))
+        return;
+    TextDocumentItem item;
+    item.setLanguageId("cpp");
+    item.setUri(DocumentUri::fromFilePath(filePath));
+    item.setText(!content.isEmpty() ? content : QString::fromUtf8(cxxFile.readAll()));
+    item.setVersion(0);
+    sendContent(DidOpenTextDocumentNotification(DidOpenTextDocumentParams(item)));
+}
+
+void ClangdClient::closeExtraFile(const Utils::FilePath &filePath)
+{
+    sendContent(DidCloseTextDocumentNotification(DidCloseTextDocumentParams(
+            TextDocumentIdentifier{DocumentUri::fromFilePath(filePath)})));
+}
+
+void ClangdClient::findUsages(TextEditor::TextDocument *document, const QTextCursor &cursor)
+{
+    if (versionNumber() < QVersionNumber(13)) {
+        symbolSupport().findUsages(document, cursor);
+        return;
+    }
+
+    QTextCursor termCursor(cursor);
+    termCursor.select(QTextCursor::WordUnderCursor);
+    const QString searchTerm = termCursor.selectedText(); // TODO: This will be wrong for e.g. operators. Use a Symbol info request to get the real symbol string.
+    if (searchTerm.isEmpty())
+        return;
+
+    ReferencesData refData;
+    refData.search = SearchResultWindow::instance()->startNewSearch(
+                tr("C++ Usages:"),
+                {},
+                searchTerm,
+                SearchResultWindow::SearchOnly,
+                SearchResultWindow::PreserveCaseDisabled,
+                "CppEditor");
+    refData.search->setFilter(new CppTools::CppSearchResultFilter);
+    connect(refData.search, &SearchResult::activated, [](const SearchResultItem& item) {
+        Core::EditorManager::openEditorAtSearchResult(item);
+    });
+    SearchResultWindow::instance()->popup(IOutputPane::ModeSwitch | IOutputPane::WithFocus);
+    refData.key = d->nextFindUsagesKey++;
+    d->runningFindUsages.insert(refData.key, refData);
+
+    const Utils::optional<MessageId> requestId = symbolSupport().findUsages(
+                document, cursor, [this, key = refData.key](const QList<Location> &locations) {
+        d->handleFindUsagesResult(key, locations);
+    });
+
+    if (!requestId) {
+        d->finishSearch(refData, false);
+        return;
+    }
+    connect(refData.search, &SearchResult::cancelled, this, [this, requestId, key = refData.key] {
+        const auto refData = d->runningFindUsages.find(key);
+        if (refData == d->runningFindUsages.end())
+            return;
+        cancelRequest(*requestId);
+        refData->setCanceled();
+        refData->search->disconnect(this);
+        d->finishSearch(*refData, true);
+    });
+}
+
+void ClangdClient::enableTesting() { d->isTesting = true; }
+
+QVersionNumber ClangdClient::versionNumber() const
+{
+    if (d->versionNumber)
+        return d->versionNumber.value();
+
+    const QRegularExpression versionPattern("^clangd version (\\d+)\\.(\\d+)\\.(\\d+).*$");
+    QTC_CHECK(versionPattern.isValid());
+    const QRegularExpressionMatch match = versionPattern.match(serverVersion());
+    if (match.isValid()) {
+        d->versionNumber.emplace({match.captured(1).toInt(), match.captured(2).toInt(),
+                                 match.captured(3).toInt()});
+    } else {
+        qCWarning(clangdLog) << "Failed to parse clangd server string" << serverVersion();
+        d->versionNumber.emplace({0});
+    }
+    return d->versionNumber.value();
+}
+
+void ClangdClient::Private::handleFindUsagesResult(quint64 key, const QList<Location> &locations)
+{
+    const auto refData = runningFindUsages.find(key);
+    if (refData == runningFindUsages.end())
+        return;
+    if (!refData->search || refData->isCanceled()) {
+        finishSearch(*refData, true);
+        return;
+    }
+    refData->search->disconnect(q);
+
+    qCDebug(clangdLog) << "found" << locations.size() << "locations";
+    if (locations.isEmpty()) {
+        finishSearch(*refData, false);
+        return;
+    }
+
+    QObject::connect(refData->search, &SearchResult::cancelled, q, [this, key] {
+        const auto refData = runningFindUsages.find(key);
+        if (refData == runningFindUsages.end())
+            return;
+        refData->setCanceled();
+        refData->search->disconnect(q);
+        for (const MessageId &id : qAsConst(refData->pendingAstRequests))
+            q->cancelRequest(id);
+        refData->pendingAstRequests.clear();
+        finishSearch(*refData, true);
+    });
+
+    for (const Location &loc : locations) // TODO: Can contain duplicates. Rather fix in clang than work around it here.
+        refData->fileData[loc.uri()].rangesAndLineText << qMakePair(loc.range(), QString()); // TODO: Can we assume that locations for the same file are grouped?
+    for (auto it = refData->fileData.begin(); it != refData->fileData.end(); ++it) {
+        const QStringList lines = SymbolSupport::getFileContents(
+                    it.key().toFilePath().toString());
+        it->fileContent = lines.join('\n');
+        for (auto &rangeWithText : it.value().rangesAndLineText) {
+            const int lineNo = rangeWithText.first.start().line();
+            if (lineNo >= 0 && lineNo < lines.size())
+                rangeWithText.second = lines.at(lineNo);
+        }
+    }
+
+    qCDebug(clangdLog) << "document count is" << refData->fileData.size();
+    if (refData->fileData.size() > 15) { // TODO: If we need to keep this, make it configurable.
+        qCDebug(clangdLog) << "skipping AST retrieval";
+        reportAllSearchResultsAndFinish(*refData);
+        return;
+    }
+
+    for (auto it = refData->fileData.begin(); it != refData->fileData.end(); ++it) {
+        const bool extraOpen = !q->documentForFilePath(it.key().toFilePath());
+        if (extraOpen)
+            q->openExtraFile(it.key().toFilePath(), it->fileContent);
+        it->fileContent.clear();
+
+        AstParams params;
+        params.setTextDocument(TextDocumentIdentifier(it.key()));
+        AstRequest request(params);
+        request.setResponseCallback([this, key, loc = it.key(), request]
+                                    (AstRequest::Response response) {
+            qCDebug(clangdLog) << "AST response for" << loc.toFilePath();
+            const auto refData = runningFindUsages.find(key);
+            if (refData == runningFindUsages.end())
+                return;
+            if (!refData->search || refData->isCanceled())
+                return;
+            ReferencesFileData &data = refData->fileData[loc];
+            const auto result = response.result();
+            if (result)
+                data.ast = *result;
+            refData->pendingAstRequests.removeOne(request.id());
+            qCDebug(clangdLog) << refData->pendingAstRequests.size()
+                               << "AST requests still pending";
+            addSearchResultsForFile(*refData, loc.toFilePath(), data);
+            refData->fileData.remove(loc);
+            if (refData->pendingAstRequests.isEmpty()) {
+                qDebug(clangdLog) << "retrieved all ASTs";
+                finishSearch(*refData, false);
+            }
+        });
+        qCDebug(clangdLog) << "requesting AST for" << it.key().toFilePath();
+        refData->pendingAstRequests << request.id();
+        q->sendContent(request);
+
+        if (extraOpen)
+            q->closeExtraFile(it.key().toFilePath());
+    }
+}
+
+void ClangdClient::Private::addSearchResultsForFile(const ReferencesData &refData,
+        const Utils::FilePath &file,
+        const ReferencesFileData &fileData)
+{
+    QList<SearchResultItem> items;
+    qCDebug(clangdLog) << file << "has valid AST:" << fileData.ast.isValid();
+    for (const auto &rangeWithText : fileData.rangesAndLineText) {
+        const Range &range = rangeWithText.first;
+        const Usage::Type usageType = fileData.ast.isValid()
+                ? getUsageType(getAstPath(fileData.ast, qAsConst(range)))
+                : Usage::Type::Other;
+        SearchResultItem item;
+        item.setUserData(int(usageType));
+        item.setStyle(CppTools::colorStyleForUsageType(usageType));
+        item.setFilePath(file);
+        item.setMainRange(SymbolSupport::convertRange(range));
+        item.setUseTextEditorFont(true);
+        item.setLineText(rangeWithText.second);
+        items << item;
+    }
+    if (isTesting)
+        emit q->foundReferences(items);
+    else
+        refData.search->addResults(items, SearchResult::AddOrdered);
+}
+
+void ClangdClient::Private::reportAllSearchResultsAndFinish(const ReferencesData &refData)
+{
+    for (auto it = refData.fileData.begin(); it != refData.fileData.end(); ++it)
+        addSearchResultsForFile(refData, it.key().toFilePath(), it.value());
+    finishSearch(refData, refData.isCanceled());
+}
+
+void ClangdClient::Private::finishSearch(const ReferencesData &refData, bool canceled)
+{
+    if (isTesting) {
+        emit q->findUsagesDone();
+    } else if (refData.search) {
+        refData.search->finishSearch(canceled);
+        refData.search->disconnect(q);
+    }
+    runningFindUsages.remove(refData.key);
+}
+
 } // namespace Internal
 } // namespace ClangCodeModel

src/plugins/clangcodemodel/clangdclient.h

@@ -27,7 +27,11 @@
 
 #include <languageclient/client.h>
 
+#include <QVersionNumber>
+
+namespace Core { class SearchResultItem; }
 namespace ProjectExplorer { class Project; }
+namespace TextEditor { class TextDocument; }
 
 namespace ClangCodeModel {
 namespace Internal {
@@ -37,11 +41,26 @@ class ClangdClient : public LanguageClient::Client
     Q_OBJECT
 public:
     ClangdClient(ProjectExplorer::Project *project, const Utils::FilePath &jsonDbDir);
+    ~ClangdClient() override;
 
-    bool isFullyIndexed() const { return m_isFullyIndexed; }
+    bool isFullyIndexed() const;
+    QVersionNumber versionNumber() const;
+
+    void openExtraFile(const Utils::FilePath &filePath, const QString &content = {});
+    void closeExtraFile(const Utils::FilePath &filePath);
+
+    void findUsages(TextEditor::TextDocument *document, const QTextCursor &cursor);
+
+    void enableTesting();
+
+signals:
+    void indexingFinished();
+    void foundReferences(const QList<Core::SearchResultItem> &items);
+    void findUsagesDone();
 
 private:
-    bool m_isFullyIndexed = false;
+    class Private;
+    Private * const d;
 };
 
 } // namespace Internal

src/plugins/clangcodemodel/clangmodelmanagersupport.cpp

@@ -64,7 +64,6 @@
 #include <utils/runextensions.h>
 
 #include <QApplication>
-#include <QFile>
 #include <QMenu>
 #include <QTextBlock>
 #include <QTimer>
@@ -281,7 +280,7 @@ void ClangModelManagerSupport::updateLanguageClient(ProjectExplorer::Project *pr
         }
         if (Client * const oldClient = clientForProject(project))
             LanguageClientManager::shutdownClient(oldClient);
-        Client * const client = createClient(project, jsonDbDir);
+        ClangdClient * const client = createClient(project, jsonDbDir);
         connect(client, &Client::initialized, this, [client, project, projectInfo, jsonDbDir] {
             using namespace ProjectExplorer;
             if (!CppTools::codeModelSettings()->useClangd())
@@ -309,18 +308,8 @@ void ClangModelManagerSupport::updateLanguageClient(ProjectExplorer::Project *pr
             if (!cxxNode)
                 return;
 
-            QFile cxxFile(cxxNode->filePath().toString());
+            client->openExtraFile(cxxNode->filePath());
-            if (!cxxFile.open(QIODevice::ReadOnly))
+            client->closeExtraFile(cxxNode->filePath());
-                return;
-            using namespace LanguageServerProtocol;
-            TextDocumentItem item;
-            item.setLanguageId("text/x-c++src");
-            item.setUri(DocumentUri::fromFilePath(cxxNode->filePath()));
-            item.setText(QString::fromUtf8(cxxFile.readAll()));
-            item.setVersion(0);
-            client->sendContent(DidOpenTextDocumentNotification(DidOpenTextDocumentParams(item)));
-            client->sendContent(DidCloseTextDocumentNotification(DidCloseTextDocumentParams(
-                    TextDocumentIdentifier{item.uri()})));
         });
 
     });
@@ -347,7 +336,9 @@ ClangdClient *ClangModelManagerSupport::clientForProject(
 ClangdClient *ClangModelManagerSupport::createClient(ProjectExplorer::Project *project,
                                                      const Utils::FilePath &jsonDbDir)
 {
-    return new ClangdClient(project, jsonDbDir);
+    const auto client = new ClangdClient(project, jsonDbDir);
+    emit createdClient(client);
+    return client;
 }
 
 void ClangModelManagerSupport::onEditorOpened(Core::IEditor *editor)

src/plugins/clangcodemodel/clangmodelmanagersupport.h

@@ -83,6 +83,9 @@ public:
 
     static ClangModelManagerSupport *instance();
 
+signals:
+    void createdClient(ClangdClient *client);
+
 private:
     void onEditorOpened(Core::IEditor *editor);
     void onEditorClosed(const QList<Core::IEditor *> &editors);

src/plugins/clangcodemodel/clangrefactoringengine.cpp

@@ -97,11 +97,9 @@ void RefactoringEngine::findUsages(const CppTools::CursorInEditor &cursor,
                 ->findUsages(cursor, std::move(callback));
         return;
     }
-    // TODO: We want to keep our "access type info" feature.
-    //       Check whether we can support it using clang 12's textDocument/ast request
     if (!client->documentOpen(cursor.textDocument()))
         client->openDocument(cursor.textDocument()); // TODO: Just a workaround
-    client->symbolSupport().findUsages(cursor.textDocument(), cursor.cursor());
+    client->findUsages(cursor.textDocument(), cursor.cursor());
 }
 
 } // namespace Internal

src/plugins/clangcodemodel/test/clangautomationutils.cpp

@@ -138,5 +138,10 @@ TextEditor::ProposalModelPtr completionResults(TextEditor::BaseTextEditor *textE
     return waitForCompletions.proposalModel;
 }
 
+QString qrcPath(const QByteArray &relativeFilePath)
+{
+    return QLatin1String(":/unittests/ClangCodeModel/") + QString::fromUtf8(relativeFilePath);
+}
+
 } // namespace Internal
 } // namespace ClangCodeModel

src/plugins/clangcodemodel/test/clangautomationutils.h

@@ -39,5 +39,7 @@ TextEditor::ProposalModelPtr completionResults(TextEditor::BaseTextEditor *textE
                                                const QStringList &includePaths = QStringList(),
                                                int timeOutInMs = 10000);
 
+QString qrcPath(const QByteArray &relativeFilePath);
+
 } // namespace Internal
 } // namespace ClangCodeModel

src/plugins/clangcodemodel/test/clangcodecompletion_test.cpp

@@ -58,9 +58,6 @@ using namespace ClangCodeModel::Internal;
 
 namespace {
 
-QString qrcPath(const QByteArray relativeFilePath)
-{ return QLatin1String(":/unittests/ClangCodeModel/") + QString::fromUtf8(relativeFilePath); }
-
 CppTools::Tests::TemporaryDir *globalTemporaryDir()
 {
     static CppTools::Tests::TemporaryDir dir;

src/plugins/clangcodemodel/test/clangdtests.cpp

@@ -0,0 +1,331 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#include "clangdtests.h"
+
+#include "clangautomationutils.h"
+#include "clangbatchfileprocessor.h"
+#include "../clangdclient.h"
+#include "../clangmodelmanagersupport.h"
+
+#include <cplusplus/FindUsages.h>
+#include <cpptools/cppcodemodelsettings.h>
+#include <cpptools/cpptoolsreuse.h>
+#include <cpptools/cpptoolstestcase.h>
+#include <coreplugin/editormanager/editormanager.h>
+#include <coreplugin/find/searchresultitem.h>
+#include <projectexplorer/kitmanager.h>
+#include <projectexplorer/project.h>
+#include <projectexplorer/projectexplorer.h>
+#include <qtsupport/qtkitinformation.h>
+#include <utils/algorithm.h>
+
+#include <QEventLoop>
+#include <QScopedPointer>
+#include <QTimer>
+#include <QtTest>
+
+using namespace CPlusPlus;
+using namespace Core;
+using namespace ProjectExplorer;
+
+namespace ClangCodeModel {
+namespace Internal {
+namespace Tests {
+
+void ClangdTests::initTestCase()
+{
+    const auto settings = CppTools::codeModelSettings();
+    const QString clangdFromEnv = qEnvironmentVariable("QTC_CLANGD");
+    if (!clangdFromEnv.isEmpty())
+        settings->setClangdFilePath(Utils::FilePath::fromString(clangdFromEnv));
+    const auto clangd = settings->clangdFilePath();
+    if (clangd.isEmpty() || !clangd.exists())
+        QSKIP("clangd binary not found");
+    settings->setUseClangd(true);
+}
+
+template <typename Signal> static bool waitForSignalOrTimeout(
+        const typename QtPrivate::FunctionPointer<Signal>::Object *sender, Signal signal)
+{
+    QTimer timer;
+    timer.setSingleShot(true);
+    timer.setInterval(timeOutInMs());
+    QEventLoop loop;
+    QObject::connect(&timer, &QTimer::timeout, &loop, &QEventLoop::quit);
+    QObject::connect(sender, signal, &loop, &QEventLoop::quit);
+    timer.start();
+    loop.exec();
+    return timer.isActive();
+}
+
+// The main point here is to test our access type categorization.
+// We do not try to stress-test clangd's "Find References" functionality; such tests belong
+// into LLVM.
+void ClangdTests::testFindReferences()
+{
+    // Find suitable kit.
+    const QList<Kit *> allKits = KitManager::kits();
+    if (allKits.isEmpty())
+        QSKIP("This test requires at least one kit to be present");
+    Kit * const kit = Utils::findOr(allKits, nullptr, [](const Kit *k) {
+        return k->isValid() && QtSupport::QtKitAspect::qtVersion(k);
+    });
+    if (!kit)
+        QSKIP("The test requires at least one valid kit with a valid Qt");
+
+    // Copy project out of qrc file, open it, and set up target.
+    CppTools::Tests::TemporaryCopiedDir testDir(qrcPath("find-usages"));
+    QVERIFY(testDir.isValid());
+    const auto openProjectResult = ProjectExplorerPlugin::openProject(
+                testDir.absolutePath("find-usages.pro"));
+    QVERIFY2(openProjectResult, qPrintable(openProjectResult.errorMessage()));
+    openProjectResult.project()->configureAsExampleProject(kit);
+
+    // Setting up the project should result in a clangd client being created.
+    // Wait until that has happened.
+    const auto modelManagerSupport = ClangModelManagerSupport::instance();
+    ClangdClient *client = modelManagerSupport->clientForProject(openProjectResult.project());
+    if (!client) {
+        QVERIFY(waitForSignalOrTimeout(modelManagerSupport,
+                                       &ClangModelManagerSupport::createdClient));
+        client = modelManagerSupport->clientForProject(openProjectResult.project());
+    }
+    QVERIFY(client);
+    client->enableTesting();
+
+    // Wait until the client is fully initialized, i.e. it's completed the handshake
+    // with the server.
+    if (!client->reachable())
+        QVERIFY(waitForSignalOrTimeout(client, &ClangdClient::initialized));
+    QVERIFY(client->reachable());
+
+    // The kind of AST support we need was introduced in LLVM 13.
+    if (client->versionNumber() < QVersionNumber(13))
+        QSKIP("Find Usages test needs clang >= 13");
+
+    // Wait for index to build.
+    if (!client->isFullyIndexed())
+        QVERIFY(waitForSignalOrTimeout(client, &ClangdClient::indexingFinished));
+    QVERIFY(client->isFullyIndexed());
+
+    // Open cpp documents.
+    struct EditorCloser {
+        static void cleanup(IEditor *editor) { EditorManager::closeEditors({editor}); }
+    };
+    const auto headerPath = Utils::FilePath::fromString(testDir.absolutePath("defs.h"));
+    QVERIFY2(headerPath.exists(), qPrintable(headerPath.toUserOutput()));
+    QScopedPointer<IEditor, EditorCloser> headerEditor(
+                EditorManager::openEditor(headerPath.toString()));
+    QVERIFY(headerEditor);
+    const auto headerDoc = qobject_cast<TextEditor::TextDocument *>(headerEditor->document());
+    QVERIFY(headerDoc);
+    QVERIFY(client->documentForFilePath(headerPath) == headerDoc);
+    const auto cppFilePath = Utils::FilePath::fromString(testDir.absolutePath("main.cpp"));
+    QVERIFY2(cppFilePath.exists(), qPrintable(cppFilePath.toUserOutput()));
+    QScopedPointer<IEditor, EditorCloser> cppFileEditor(
+                EditorManager::openEditor(cppFilePath.toString()));
+    QVERIFY(cppFileEditor);
+    const auto cppDoc = qobject_cast<TextEditor::TextDocument *>(cppFileEditor->document());
+    QVERIFY(cppDoc);
+    QVERIFY(client->documentForFilePath(cppFilePath) == cppDoc);
+
+    // ... and we're ready to go.
+    QList<SearchResultItem> searchResults;
+    connect(client, &ClangdClient::foundReferences, this,
+            [&searchResults](const QList<SearchResultItem> &results) {
+        if (results.isEmpty())
+            return;
+        if (results.first().path().first().endsWith("defs.h"))
+            searchResults = results + searchResults; // Guarantee expected file order.
+        else
+            searchResults += results;
+    });
+
+#define FIND_USAGES(doc, pos) do { \
+    QTextCursor cursor((doc)->document()); \
+    cursor.setPosition((pos)); \
+    searchResults.clear(); \
+    client->findUsages((doc), cursor); \
+    QVERIFY(waitForSignalOrTimeout(client, &ClangdClient::findUsagesDone)); \
+} while (false)
+
+#define EXPECT_RESULT(index, lne, col, type) \
+    QCOMPARE(searchResults.at(index).mainRange().begin.line, lne); \
+    QCOMPARE(searchResults.at(index).mainRange().begin.column, col); \
+    QCOMPARE(searchResults.at(index).userData().toInt(), int(type))
+
+    // All kinds of checks involving a struct member.
+    FIND_USAGES(headerDoc, 55);
+    QCOMPARE(searchResults.size(), 32);
+    EXPECT_RESULT(0, 2, 17, Usage::Type::Read);
+    EXPECT_RESULT(1, 3, 15, Usage::Type::Declaration);
+    EXPECT_RESULT(2, 6, 17, Usage::Type::WritableRef);
+    EXPECT_RESULT(3, 8, 11, Usage::Type::WritableRef);
+    EXPECT_RESULT(4, 9, 13, Usage::Type::WritableRef);
+    EXPECT_RESULT(5, 10, 12, Usage::Type::WritableRef);
+    EXPECT_RESULT(6, 11, 13, Usage::Type::WritableRef);
+    EXPECT_RESULT(7, 12, 14, Usage::Type::WritableRef);
+    EXPECT_RESULT(8, 13, 26, Usage::Type::WritableRef);
+    EXPECT_RESULT(9, 14, 23, Usage::Type::Read);
+    EXPECT_RESULT(10, 15, 14, Usage::Type::Read);
+    EXPECT_RESULT(11, 16, 24, Usage::Type::WritableRef);
+    EXPECT_RESULT(12, 17, 15, Usage::Type::WritableRef);
+    EXPECT_RESULT(13, 18, 22, Usage::Type::Read);
+    EXPECT_RESULT(14, 19, 12, Usage::Type::WritableRef);
+    EXPECT_RESULT(15, 20, 12, Usage::Type::Read);
+    EXPECT_RESULT(16, 21, 13, Usage::Type::WritableRef);
+    EXPECT_RESULT(17, 22, 13, Usage::Type::Read);
+    EXPECT_RESULT(18, 23, 12, Usage::Type::Read);
+    EXPECT_RESULT(19, 42, 20, Usage::Type::Read);
+    EXPECT_RESULT(20, 44, 15, Usage::Type::Read);
+    EXPECT_RESULT(21, 47, 15, Usage::Type::Write);
+    EXPECT_RESULT(22, 50, 11, Usage::Type::Read);
+    EXPECT_RESULT(23, 51, 11, Usage::Type::Write);
+    EXPECT_RESULT(24, 52, 9, Usage::Type::Write);
+    EXPECT_RESULT(25, 53, 7, Usage::Type::Write);
+    EXPECT_RESULT(26, 56, 7, Usage::Type::Write);
+    EXPECT_RESULT(27, 56, 25, Usage::Type::Other);
+    EXPECT_RESULT(28, 58, 13, Usage::Type::Read);
+    EXPECT_RESULT(29, 58, 25, Usage::Type::Read);
+    EXPECT_RESULT(30, 59, 7, Usage::Type::Write);
+    EXPECT_RESULT(31, 59, 24, Usage::Type::Read);
+
+    // Detect constructor member initialization as a write access.
+    FIND_USAGES(headerDoc, 68);
+    QCOMPARE(searchResults.size(), 2);
+    EXPECT_RESULT(0, 2, 10, Usage::Type::Write);
+    EXPECT_RESULT(1, 4, 8, Usage::Type::Declaration);
+
+    // Detect direct member initialization.
+    FIND_USAGES(headerDoc, 101);
+    QCOMPARE(searchResults.size(), 2);
+    EXPECT_RESULT(0, 5, 21, Usage::Type::Initialization);
+    EXPECT_RESULT(1, 45, 16, Usage::Type::Read);
+
+    // Make sure that pure virtual declaration is not mistaken for an assignment.
+    FIND_USAGES(headerDoc, 420);
+    QCOMPARE(searchResults.size(), 3); // FIXME: The override gets reported twice. clang bug?
+    EXPECT_RESULT(0, 17, 17, Usage::Type::Declaration);
+    EXPECT_RESULT(1, 21, 9, Usage::Type::Declaration);
+    EXPECT_RESULT(2, 21, 9, Usage::Type::Declaration);
+
+    // References to pointer variable.
+    FIND_USAGES(cppDoc, 52);
+    QCOMPARE(searchResults.size(), 11);
+    EXPECT_RESULT(0, 6, 10, Usage::Type::Initialization);
+    EXPECT_RESULT(1, 8, 4, Usage::Type::Write);
+    EXPECT_RESULT(2, 10, 4, Usage::Type::Write);
+    EXPECT_RESULT(3, 24, 5, Usage::Type::Write);
+    EXPECT_RESULT(4, 25, 11, Usage::Type::WritableRef);
+    EXPECT_RESULT(5, 26, 11, Usage::Type::Read);
+    EXPECT_RESULT(6, 27, 10, Usage::Type::WritableRef);
+    EXPECT_RESULT(7, 28, 10, Usage::Type::Read);
+    EXPECT_RESULT(8, 29, 11, Usage::Type::Read);
+    EXPECT_RESULT(9, 30, 15, Usage::Type::WritableRef);
+    EXPECT_RESULT(10, 31, 22, Usage::Type::Read);
+
+    // References to struct variable, directly and via members.
+    FIND_USAGES(cppDoc, 39);
+    QCOMPARE(searchResults.size(), 34);
+    EXPECT_RESULT(0, 5, 7, Usage::Type::Declaration);
+    EXPECT_RESULT(1, 6, 15, Usage::Type::WritableRef);
+    EXPECT_RESULT(2, 8, 9, Usage::Type::WritableRef);
+    EXPECT_RESULT(3, 9, 11, Usage::Type::WritableRef);
+    EXPECT_RESULT(4, 11, 4, Usage::Type::Write);
+    EXPECT_RESULT(5, 11, 11, Usage::Type::WritableRef);
+    EXPECT_RESULT(6, 12, 12, Usage::Type::WritableRef);
+    EXPECT_RESULT(7, 13, 6, Usage::Type::Write);
+    EXPECT_RESULT(8, 14, 21, Usage::Type::Read);
+    EXPECT_RESULT(9, 15, 4, Usage::Type::Write);
+    EXPECT_RESULT(10, 15, 12, Usage::Type::Read);
+    EXPECT_RESULT(11, 16, 22, Usage::Type::WritableRef);
+    EXPECT_RESULT(12, 17, 13, Usage::Type::WritableRef);
+    EXPECT_RESULT(13, 18, 20, Usage::Type::Read);
+    EXPECT_RESULT(14, 19, 10, Usage::Type::WritableRef);
+    EXPECT_RESULT(15, 20, 10, Usage::Type::Read);
+    EXPECT_RESULT(16, 21, 11, Usage::Type::WritableRef);
+    EXPECT_RESULT(17, 22, 11, Usage::Type::Read);
+    EXPECT_RESULT(18, 23, 10, Usage::Type::Read);
+    EXPECT_RESULT(19, 32, 4, Usage::Type::Write);
+    EXPECT_RESULT(20, 33, 23, Usage::Type::WritableRef);
+    EXPECT_RESULT(21, 34, 23, Usage::Type::Read);
+    EXPECT_RESULT(22, 35, 15, Usage::Type::WritableRef);
+    EXPECT_RESULT(23, 36, 22, Usage::Type::WritableRef);
+    EXPECT_RESULT(24, 37, 4, Usage::Type::Read);
+    EXPECT_RESULT(25, 38, 4, Usage::Type::WritableRef);
+    EXPECT_RESULT(26, 39, 6, Usage::Type::WritableRef);
+    EXPECT_RESULT(27, 40, 4, Usage::Type::Read);
+    EXPECT_RESULT(28, 41, 4, Usage::Type::WritableRef);
+    EXPECT_RESULT(29, 42, 4, Usage::Type::Read);
+    EXPECT_RESULT(30, 42, 18, Usage::Type::Read);
+    EXPECT_RESULT(31, 43, 11, Usage::Type::Write);
+    EXPECT_RESULT(32, 54, 4, Usage::Type::Other);
+    EXPECT_RESULT(33, 55, 4, Usage::Type::Other);
+
+    // References to struct type.
+    FIND_USAGES(headerDoc, 7);
+    QCOMPARE(searchResults.size(), 18);
+    EXPECT_RESULT(0, 1, 7, Usage::Type::Declaration);
+    EXPECT_RESULT(1, 2, 4, Usage::Type::Declaration);
+    EXPECT_RESULT(2, 20, 19, Usage::Type::Other);
+
+    // These are conceptually questionable, as S is a type and thus we cannot "read from"
+    // or "write to" it. But it probably matches the intuitive user expectation.
+    EXPECT_RESULT(3, 10, 9, Usage::Type::WritableRef);
+    EXPECT_RESULT(4, 12, 4, Usage::Type::Write);
+    EXPECT_RESULT(5, 44, 12, Usage::Type::Read);
+    EXPECT_RESULT(6, 45, 13, Usage::Type::Read);
+    EXPECT_RESULT(7, 47, 12, Usage::Type::Write);
+    EXPECT_RESULT(8, 50, 8, Usage::Type::Read);
+    EXPECT_RESULT(9, 51, 8, Usage::Type::Write);
+    EXPECT_RESULT(10, 52, 6, Usage::Type::Write);
+    EXPECT_RESULT(11, 53, 4, Usage::Type::Write);
+    EXPECT_RESULT(12, 56, 4, Usage::Type::Write);
+    EXPECT_RESULT(13, 56, 22, Usage::Type::Other);
+    EXPECT_RESULT(14, 58, 10, Usage::Type::Read);
+    EXPECT_RESULT(15, 58, 22, Usage::Type::Read);
+    EXPECT_RESULT(16, 59, 4, Usage::Type::Write);
+    EXPECT_RESULT(17, 59, 21, Usage::Type::Read);
+
+    // References to subclass type.
+    FIND_USAGES(headerDoc, 450);
+    QCOMPARE(searchResults.size(), 4);
+    EXPECT_RESULT(0, 20, 7, Usage::Type::Declaration);
+    EXPECT_RESULT(1, 5, 4, Usage::Type::Other);
+    EXPECT_RESULT(2, 13, 21, Usage::Type::Other);
+    EXPECT_RESULT(3, 32, 8, Usage::Type::Other);
+
+    // References to array variables.
+    FIND_USAGES(cppDoc, 1134);
+    QCOMPARE(searchResults.size(), 3);
+    EXPECT_RESULT(0, 57, 8, Usage::Type::Declaration);
+    EXPECT_RESULT(1, 58, 4, Usage::Type::Write);
+    EXPECT_RESULT(2, 59, 15, Usage::Type::Read);
+}
+
+} // namespace Tests
+} // namespace Internal
+} // namespace ClangCodeModel

src/plugins/clangcodemodel/test/clangdtests.h

@@ -0,0 +1,47 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#pragma once
+
+#include <QObject>
+
+namespace ClangCodeModel {
+namespace Internal {
+namespace Tests {
+
+class ClangdTests : public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void initTestCase();
+
+    void testFindReferences();
+};
+
+} // namespace Tests
+} // namespace Internal
+} // namespace ClangCodeModel
+

src/plugins/clangcodemodel/test/data/clangtestdata.qrc

@@ -29,5 +29,8 @@
         <file>membercompletion-friend.cpp</file>
         <file>functionCompletionFiltered.cpp</file>
         <file>functionCompletionFiltered2.cpp</file>
+        <file>find-usages/defs.h</file>
+        <file>find-usages/main.cpp</file>
+        <file>find-usages/find-usages.pro</file>
     </qresource>
 </RCC>

src/plugins/clangcodemodel/test/data/find-usages/defs.h

@@ -0,0 +1,28 @@
+struct S {
+    S() : value2(value) {}
+    static int value;
+    int value2 : 2;
+    static const int value3 = 0;
+    static void *p;
+    static const void *p2;
+    struct Nested {
+        int constFunc() const;
+        void constFunc(int) const;
+        void nonConstFunc();
+    } n;
+    Nested constFunc() const;
+    void nonConstFunc();
+    static void staticFunc1() {}
+    static void staticFunc2();
+    virtual void pureVirtual() = 0;
+};
+
+struct S2 : public S {
+    void pureVirtual() override {}
+};
+
+void func1(int &);
+void func2(const int &);
+void func3(int *);
+void func4(const int *);
+void func5(int);

src/plugins/clangcodemodel/test/data/find-usages/find-usages.pro

@@ -0,0 +1,4 @@
+TEMPLATE = app
+QT = core
+HEADERS = defs.h
+SOURCES = main.cpp

src/plugins/clangcodemodel/test/data/find-usages/main.cpp

@@ -0,0 +1,60 @@
+#include "defs.h"
+
+int main()
+{
+    S2 s;
+    auto *p = &s.value;
+    int **pp;
+    p = &s.value;
+    *pp = &s.value;
+    p = &S::value;
+    s.p = &s.value;
+    S::p = &s.value;
+    (&s)->p = &((new S2)->value);
+    const int *p2 = &s.value;
+    s.p2 = &s.value;
+    int * const p3 = &s.value;
+    int &r = s.value;
+    const int &cr = s.value;
+    func1(s.value);
+    func2(s.value);
+    func3(&s.value);
+    func4(&s.value);
+    func5(s.value);
+    *p = 5;
+    func1(*p);
+    func2(*p);
+    func3(p);
+    func4(p);
+    func5(*p);
+    int &r2 = *p;
+    const int &cr2 = *p;
+    s = S2();
+    auto * const ps = &s;
+    const auto *ps2 = &s;
+    auto &pr = s;
+    const auto pr2 = &s;
+    s.constFunc().nonConstFunc();
+    s.nonConstFunc();
+    (&s)->nonConstFunc();
+    s.n.constFunc();
+    s.n.nonConstFunc();
+    s.n.constFunc(s.value);
+    delete s.p;
+    switch (S::value) {
+        case S::value3: break;
+    }
+    switch (S::value = 5) {
+        default: break;
+    }
+    if (S::value) {}
+    if (S::value = 0) {}
+    ++S::value;
+    S::value--;
+    s.staticFunc1();
+    s.staticFunc2();
+    S::value = sizeof S::value;
+    int array[3];
+    array[S::value] = S::value;
+    S::value = array[S::value];
+}