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//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists purely as an
// implementation detail.  This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.

#ifndef Patternist_LetClause_H
#define Patternist_LetClause_H

#include "qpaircontainer_p.h"
#include "qvariabledeclaration_p.h"

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

namespace QPatternist
{

    /**
     * @short Represents a <tt>let</tt>-clause, but is only used at compile
     * time.
     *
     * LetClause is inserted into the AST tree for the single purpose of
     * ensuring that the focus is correct for the binding expression. Once
     * that is done, LetClause sometimes rewrites itself to its
     * <tt>return</tt> expression, and the ExpressionVariableReference will
     * handle the evaluation of the variable.
     *
     * @author Frans Englich <fenglich@trolltech.com>
     * @ingroup Patternist_expressions
     */
    class LetClause : public PairContainer
    {
    public:
        LetClause(const Expression::Ptr &operand1,
                  const Expression::Ptr &operand2,
                  const VariableDeclaration::Ptr &decl);

        virtual Item::Iterator::Ptr evaluateSequence(const DynamicContext::Ptr &context) const;
        virtual Item evaluateSingleton(const DynamicContext::Ptr &context) const;
        virtual bool evaluateEBV(const DynamicContext::Ptr &context) const;
        virtual void evaluateToSequenceReceiver(const DynamicContext::Ptr &context) const;

        virtual SequenceType::List expectedOperandTypes() const;
        virtual Expression::Ptr typeCheck(const StaticContext::Ptr &context,
                                          const SequenceType::Ptr &reqType);
        virtual SequenceType::Ptr staticType() const;
        virtual Properties properties() const;
        virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const;
        virtual ID id() const;

    private:
        inline DynamicContext::Ptr bindVariable(const DynamicContext::Ptr &context) const;

        const VariableDeclaration::Ptr m_varDecl;
    };
}

QT_END_NAMESPACE

QT_END_HEADER

#endif