ClangCodeModel: Use dedicated TU for code related to the clangd AST

The clangdclient.cpp file is rather large, and the AST stuff is a nicely
self-contained chunk of code to move out.
No functional changes.

Change-Id: I0240413f561f5c67ca5ee310b5c4253ffa62fdae
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangdast.h

@@ -0,0 +1,123 @@
+/****************************************************************************
+**
+** Copyright (C) 2022 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 <coreplugin/helpitem.h>
+#include <languageserverprotocol/jsonobject.h>
+
+#include <functional>
+
+namespace LanguageClient { class Client; }
+namespace LanguageServerProtocol {
+class MessageId;
+class Position;
+class Range;
+}
+namespace Utils { class FilePath; }
+
+QT_BEGIN_NAMESPACE
+class QStringView;
+QT_END_NAMESPACE
+
+namespace ClangCodeModel::Internal {
+
+// string view helpers
+QStringView subViewLen(const QString &s, qsizetype start, qsizetype length);
+QStringView subViewEnd(const QString &s, qsizetype start, qsizetype end);
+
+class ClangdAstNode : public LanguageServerProtocol::JsonObject
+{
+public:
+    using JsonObject::JsonObject;
+
+    // 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;
+
+    // The specific kind of node, such as “BinaryOperator”. Corresponds to clang’s concrete
+    // node class, with Expr etc suffix dropped.
+    QString kind() const;
+
+    // Brief additional details, such as ‘||’. Information present here depends on the node kind.
+    Utils::optional<QString> detail() const;
+
+    // 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;
+
+    // The part of the code that produced this node. Missing for implicit nodes, nodes produced
+    // by macro expansion, etc.
+    LanguageServerProtocol::Range range() const;
+
+    // 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<ClangdAstNode>> children() const;
+
+    bool hasRange() const;
+    bool arcanaContains(const QString &s) const;
+    bool detailIs(const QString &s) const { return detail() && *detail() == s; }
+    bool isMemberFunctionCall() const;
+    bool isPureVirtualDeclaration() const;
+    bool isPureVirtualDefinition() const;
+    bool mightBeAmbiguousVirtualCall() const;
+    bool isNamespace() const { return role() == "declaration" && kind() == "Namespace"; }
+    bool isTemplateParameterDeclaration() const;;
+    QString type() const;
+    QString typeFromPos(const QString &s, int pos) const;
+    Core::HelpItem::Category qdocCategoryForDeclaration(Core::HelpItem::Category fallback);
+
+    // 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 used as lvalues
+    // or rvalues.
+    bool hasConstType() const;
+
+    bool childContainsRange(int index, const LanguageServerProtocol::Range &range) const;
+    bool hasChildWithRole(const QString &role) const;
+    QString operatorString() const;
+
+    enum class FileStatus { Ours, Foreign, Mixed, Unknown };
+    FileStatus fileStatus(const Utils::FilePath &thisFile) const;
+
+    // For debugging.
+    void print(int indent = 0) const;
+
+    bool isValid() const override;
+};
+using ClangdAstPath = QList<ClangdAstNode>;
+
+ClangdAstPath getAstPath(const ClangdAstNode &root, const LanguageServerProtocol::Range &range);
+ClangdAstPath getAstPath(const ClangdAstNode &root, const LanguageServerProtocol::Position &pos);
+
+using AstHandler = std::function<void(const ClangdAstNode &node,
+                                      const LanguageServerProtocol::MessageId &requestId)>;
+LanguageServerProtocol::MessageId requestAst(LanguageClient::Client *client,
+        const Utils::FilePath &filePath, const LanguageServerProtocol::Range range,
+        const AstHandler &handler);
+
+} // namespace ClangCodeModel::Internal
+