src/log4net/Diagnostics/CodeAnalysis/NotNullWhenAttribute.cs

#region Apache License
//
// Licensed to the Apache Software Foundation (ASF) under one or more 
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership. 
// The ASF licenses this file to you under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with 
// the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#endregion

// inspired by https://github.com/dotnet/runtime/blob/main/src/libraries/System.Private.CoreLib/src/System/Diagnostics/CodeAnalysis/NullableAttributes.cs

#if !NET6_0_OR_GREATER
namespace System.Diagnostics.CodeAnalysis;

/// <summary>
/// Specifies that when a method returns ReturnValue,
/// the parameter will not be null even if the corresponding type allows it.
/// </summary>
[AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
internal sealed class NotNullWhenAttribute : Attribute
{
  /// <summary>
  /// Initializes the attribute with the specified return value condition.
  /// </summary>
  /// <param name="returnValue">
  /// The return value condition.
  /// If the method returns this value, the associated parameter will not be null.</param>
  public NotNullWhenAttribute(bool returnValue) => ReturnValue = returnValue;

  /// <summary>
  /// Gets the return value condition.
  /// </summary>
  public bool ReturnValue { get; }
}
#endif