Expression1.cs

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using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Dynamic.Utils;
 
namespace System.Linq.Expressions;
 
internal sealed class Expression1<TDelegate> : Expression<TDelegate>
{
    private object _par0;
 
    internal override int ParameterCount => 1;
 
    public Expression1(Expression body, ParameterExpression par0)
        : base(body)
    {
        _par0 = par0;
    }
 
    internal override ParameterExpression GetParameter(int index)
    {
        if (index == 0)
        {
            return ExpressionUtils.ReturnObject<ParameterExpression>(_par0);
        }
        throw Error.ArgumentOutOfRange("index");
    }
 
    internal override bool SameParameters(ICollection<ParameterExpression> parameters)
    {
        if (parameters != null && parameters.Count == 1)
        {
            using (IEnumerator<ParameterExpression> enumerator = parameters.GetEnumerator())
            {
                enumerator.MoveNext();
                return enumerator.Current == ExpressionUtils.ReturnObject<ParameterExpression>(_par0);
            }
        }
        return false;
    }
 
    internal override ReadOnlyCollection<ParameterExpression> GetOrMakeParameters()
    {
        return ExpressionUtils.ReturnReadOnly(this, ref _par0);
    }
 
    internal override Expression<TDelegate> Rewrite(Expression body, ParameterExpression[] parameters)
    {
        if (parameters != null)
        {
            return Expression.Lambda<TDelegate>(body, parameters);
        }
        return Expression.Lambda<TDelegate>(body, new ParameterExpression[1] { ExpressionUtils.ReturnObject<ParameterExpression>(_par0) });
    }
}