naps2/NAPS2.Escl.Server/CompilerAttributes.cs

// https://sergiopedri.medium.com/enabling-and-using-c-9-features-on-older-and-unsupported-runtimes-ce384d8debb
// ReSharper disable once CheckNamespace

namespace System.Runtime.CompilerServices
{
    internal static class IsExternalInit
    {
    }

    /// <summary>Specifies that a type has required members or that a member is required.</summary>
    [AttributeUsage(
        AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Field | AttributeTargets.Property,
        AllowMultiple = false, Inherited = false)]
    internal sealed class RequiredMemberAttribute : Attribute
    {
    }

    /// <summary>
    /// Indicates that compiler support for a particular feature is required for the location where this attribute is applied.
    /// </summary>
    [AttributeUsage(AttributeTargets.All, AllowMultiple = true, Inherited = false)]
    internal sealed class CompilerFeatureRequiredAttribute : Attribute
    {
        public CompilerFeatureRequiredAttribute(string featureName)
        {
            FeatureName = featureName;
        }

        /// <summary>
        /// The name of the compiler feature.
        /// </summary>
        public string FeatureName { get; }

        /// <summary>
        /// If true, the compiler can choose to allow access to the location where this attribute is applied if it does not understand <see cref="FeatureName"/>.
        /// </summary>
        public bool IsOptional { get; init; }

        /// <summary>
        /// The <see cref="FeatureName"/> used for the ref structs C# feature.
        /// </summary>
        public const string RefStructs = nameof(RefStructs);

        /// <summary>
        /// The <see cref="FeatureName"/> used for the required members C# feature.
        /// </summary>
        public const string RequiredMembers = nameof(RequiredMembers);
    }
}

namespace System.Diagnostics.CodeAnalysis
{
    /// <summary>
    /// Specifies that this constructor sets all required members for the current type, and callers
    /// do not need to set any required members themselves.
    /// </summary>
    [AttributeUsage(AttributeTargets.Constructor, AllowMultiple = false, Inherited = false)]
    internal sealed class SetsRequiredMembersAttribute : Attribute
    {
    }
}