Clang: Use completion through backend process

This makes us independent of libclang crashes for completion.
Re-parsing for highlighting still happens in the Qt Creator process.

Run in verbose mode:
    qtc.clangcodemodel.ipc=true

Run tests:
    -test "ClangCodeModel"

Task-number: QTCREATORBUG-14108
Task-number: QTCREATORBUG-12819
Change-Id: Id3e95bd2afdb6508bbd1d35fddc69534a909b905
Reviewed-by: Marco Bubke <marco.bubke@theqtcompany.com>

src/plugins/clangcodemodel/clangcompletioncontextanalyzer.h

@@ -0,0 +1,94 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd.
+** Contact: http://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 http://www.qt.io/terms-conditions.  For further information
+** use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file.  Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, The Qt Company gives you certain additional
+** rights.  These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+****************************************************************************/
+
+#ifndef CLANGCOMPLETIONCONTEXTANALYZER_H
+#define CLANGCOMPLETIONCONTEXTANALYZER_H
+
+#include <cplusplus/Token.h>
+
+#include <QString>
+
+namespace TextEditor { class AssistInterface; }
+
+namespace ClangCodeModel {
+namespace Internal {
+
+class ClangCompletionContextAnalyzer
+{
+public:
+    ClangCompletionContextAnalyzer(const TextEditor::AssistInterface *assistInterface,
+                                   CPlusPlus::LanguageFeatures languageFeatures);
+    void analyze();
+
+    enum CompletionAction {
+        PassThroughToLibClang,
+        PassThroughToLibClangAfterLeftParen,
+        CompleteDoxygenKeyword,
+        CompleteIncludePath,
+        CompletePreprocessorDirective,
+        CompleteSignal,
+        CompleteSlot
+    };
+    CompletionAction completionAction() const { return m_completionAction; }
+    unsigned completionOperator() const { return m_completionOperator; }
+    int positionForProposal() const { return m_positionForProposal; }
+    int positionForClang() const { return m_positionForClang; }
+    int positionEndOfExpression() const { return m_positionEndOfExpression; }
+
+    QString functionName() const { return m_functionName; }
+
+private:
+    ClangCompletionContextAnalyzer();
+
+    struct FunctionInfo { int functionNamePosition; QString functionName; };
+    FunctionInfo analyzeFunctionCall(int endOfExpression) const;
+
+    int findStartOfName(int position = -1) const;
+    int skipPrecedingWhitespace(int position) const;
+    int startOfOperator(int position, unsigned *kind, bool wantFunctionCall) const;
+
+    void setActionAndClangPosition(CompletionAction action, int position);
+
+    const TextEditor::AssistInterface * const m_interface; // Not owned
+    const CPlusPlus::LanguageFeatures m_languageFeatures; // TODO: Get from assistInterface?!
+
+    // Results
+    CompletionAction m_completionAction = PassThroughToLibClang;
+    unsigned m_completionOperator = CPlusPlus::T_EOF_SYMBOL;
+    int m_positionForProposal = -1;
+    int m_positionForClang = -1;
+    int m_positionEndOfExpression = -1;
+    QString m_functionName;
+};
+
+} // namespace Internal
+} // namespace ClangCodeModel
+
+#endif // CLANGCOMPLETIONCONTEXTANALYZER_H