Block4.cs

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using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Dynamic.Utils;
 
namespace System.Linq.Expressions;
 
internal sealed class Block4 : BlockExpression
{
    private object _arg0;
 
    private readonly Expression _arg1;
 
    private readonly Expression _arg2;
 
    private readonly Expression _arg3;
 
    internal override int ExpressionCount => 4;
 
    internal Block4(Expression arg0, Expression arg1, Expression arg2, Expression arg3)
    {
        _arg0 = arg0;
        _arg1 = arg1;
        _arg2 = arg2;
        _arg3 = arg3;
    }
 
    internal override bool SameExpressions(ICollection<Expression> expressions)
    {
        if (expressions.Count == 4)
        {
            if (_arg0 is ReadOnlyCollection<Expression> current)
            {
                return ExpressionUtils.SameElements(expressions, current);
            }
            using IEnumerator<Expression> enumerator = expressions.GetEnumerator();
            enumerator.MoveNext();
            if (enumerator.Current == _arg0)
            {
                enumerator.MoveNext();
                if (enumerator.Current == _arg1)
                {
                    enumerator.MoveNext();
                    if (enumerator.Current == _arg2)
                    {
                        enumerator.MoveNext();
                        return enumerator.Current == _arg3;
                    }
                }
            }
        }
        return false;
    }
 
    internal override Expression GetExpression(int index)
    {
        return index switch
        {
            0 => ExpressionUtils.ReturnObject<Expression>(_arg0), 
            1 => _arg1, 
            2 => _arg2, 
            3 => _arg3, 
            _ => throw Error.ArgumentOutOfRange("index"), 
        };
    }
 
    internal override ReadOnlyCollection<Expression> GetOrMakeExpressions()
    {
        return BlockExpression.ReturnReadOnlyExpressions(this, ref _arg0);
    }
 
    internal override BlockExpression Rewrite(ReadOnlyCollection<ParameterExpression> variables, Expression[] args)
    {
        return new Block4(args[0], args[1], args[2], args[3]);
    }
}