ClangCodeModel: Do not call FilePath::exists() on random strings

Fixes: QTCREATORBUG-29356
Change-Id: I6f4d89a6823829a7ecf16200786621321fea61a5
Reviewed-by: David Schulz <david.schulz@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/plugins/clangcodemodel/clangdclient.cpp

@@ -1114,7 +1114,23 @@ void ClangdClient::gatherHelpItemForTooltip(const HoverRequest::Response &hoverR
                 cleanString.remove('`');
                 const QStringList lines = cleanString.trimmed().split('\n');
                 for (const QString &line : lines) {
-                    const auto markupFilePath = Utils::FilePath::fromUserInput(line.simplified());
+                    const QString possibleFilePath = line.simplified();
+                    const auto looksLikeFilePath = [&] {
+                        if (possibleFilePath.length() < 3)
+                            return false;
+                        if (osType() == OsTypeWindows) {
+                            if (possibleFilePath.startsWith(R"(\\)"))
+                                return true;
+                            return possibleFilePath.front().isLetter()
+                                    && possibleFilePath.at(1) == ':'
+                                    && possibleFilePath.at(2) == '\\';
+                        }
+                        return possibleFilePath.front() == '/'
+                                && possibleFilePath.at(1).isLetterOrNumber();
+                    };
+                    if (!looksLikeFilePath())
+                        continue;
+                    const auto markupFilePath = Utils::FilePath::fromUserInput(possibleFilePath);
                     if (markupFilePath.exists()) {
                         d->setHelpItemForTooltip(hoverResponse.id(),
                                                  filePath,

src/plugins/languageclient/client.cpp

@@ -2169,6 +2169,11 @@ DocumentUri Client::hostPathToServerUri(const Utils::FilePath &path) const
     });
 }
 
+OsType Client::osType() const
+{
+    return d->m_serverDeviceTemplate.osType();
+}
+
 void Client::registerCustomMethod(const QString &method, const CustomMethodHandler &handler)
 {
     d->m_customHandlers.insert(method, handler);

src/plugins/languageclient/client.h

@@ -168,6 +168,7 @@ public:
     LanguageServerProtocol::DocumentUri::PathMapper hostPathMapper() const;
     Utils::FilePath serverUriToHostPath(const LanguageServerProtocol::DocumentUri &uri) const;
     LanguageServerProtocol::DocumentUri hostPathToServerUri(const Utils::FilePath &path) const;
+    Utils::OsType osType() const;
 
     // custom methods
     using CustomMethodHandler = std::function<void(