ContractUtils.cs

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using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Linq.Expressions;
 
namespace System.Dynamic.Utils;
 
internal static class ContractUtils
{
    [ExcludeFromCodeCoverage(Justification = "Unreachable")]
    public static Exception Unreachable => new InvalidOperationException("Code supposed to be unreachable");
 
    public static void Requires([DoesNotReturnIf(false)] bool precondition, string paramName)
    {
        if (!precondition)
        {
            throw Error.InvalidArgumentValue(paramName);
        }
    }
 
    public static void RequiresNotNull(object value, string paramName)
    {
        if (value == null)
        {
            throw new ArgumentNullException(paramName);
        }
    }
 
    public static void RequiresNotNull(object value, string paramName, int index)
    {
        if (value == null)
        {
            throw new ArgumentNullException(GetParamName(paramName, index));
        }
    }
 
    public static void RequiresNotEmpty<T>(ICollection<T> collection, string paramName)
    {
        RequiresNotNull(collection, paramName);
        if (collection.Count == 0)
        {
            throw Error.NonEmptyCollectionRequired(paramName);
        }
    }
 
    public static void RequiresNotNullItems<T>(IList<T> array, string arrayName)
    {
        RequiresNotNull(array, arrayName);
        int i = 0;
        for (int count = array.Count; i < count; i++)
        {
            if (array[i] == null)
            {
                throw new ArgumentNullException(GetParamName(arrayName, i));
            }
        }
    }
 
    private static string GetParamName(string paramName, int index)
    {
        if (index < 0)
        {
            return paramName;
        }
        return $"{paramName}[{index}]";
    }
 
    public static void RequiresArrayRange<T>(IList<T> array, int offset, int count, string offsetName, string countName)
    {
        if (count < 0)
        {
            throw new ArgumentOutOfRangeException(countName);
        }
        if (offset < 0 || array.Count - offset < count)
        {
            throw new ArgumentOutOfRangeException(offsetName);
        }
    }
}