Madness (#27)

* Add MemberNotNullWhenAttribute

* Fix file header

JustArchiNET.Madness/MemberNotNullWhenMadness/MemberNotNullWhenAttribute.cs

@@ -0,0 +1,67 @@
+//                             _         __  __
+//  ___  ___   ___  _ __    __| |  __ _ |  \/  |
+// / __|/ __| / _ \| '_ \  / _` | / _` || |\/| |
+// \__ \\__ \|  __/| | | || (_| || (_| || |  | |
+// |___/|___/ \___||_| |_| \__,_| \__,_||_|  |_|
+// |
+// Copyright 2021-2022 Łukasz "JustArchi" Domeradzki
+// Contact: [email protected]
+// |
+// Licensed 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.
+
+using System;
+using JetBrains.Annotations;
+using JustArchiNET.Madness.Helpers;
+
+namespace JustArchiNET.Madness.MemberNotNullWhenMadness;
+
+[MadnessType(EMadnessType.Implementation)]
+[PublicAPI]
+[AttributeUsage(AttributeTargets.Method | AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
+public sealed class MemberNotNullWhenAttribute : Attribute {
+	/// <summary>Gets the return value condition.</summary>
+	[MadnessType(EMadnessType.Implementation)]
+	public bool ReturnValue { get; }
+
+	/// <summary>Gets field or property member names.</summary>
+	[MadnessType(EMadnessType.Implementation)]
+	public string[] Members { get; }
+
+	/// <summary>Initializes the attribute with the specified return value condition and a field or property member.</summary>
+	/// <param name="returnValue">
+	/// The return value condition. If the method returns this value, the associated parameter will not be null.
+	/// </param>
+	/// <param name="member">
+	/// The field or property member that is promised to be not-null.
+	/// </param>
+	[MadnessType(EMadnessType.Implementation)]
+	public MemberNotNullWhenAttribute(bool returnValue, string member)
+	{
+		ReturnValue = returnValue;
+		Members = new[] { member };
+	}
+
+	/// <summary>Initializes the attribute with the specified return value condition and list of field and property members.</summary>
+	/// <param name="returnValue">
+	/// The return value condition. If the method returns this value, the associated parameter will not be null.
+	/// </param>
+	/// <param name="members">
+	/// The list of field and property members that are promised to be not-null.
+	/// </param>
+	[MadnessType(EMadnessType.Implementation)]
+	public MemberNotNullWhenAttribute(bool returnValue, params string[] members)
+	{
+		ReturnValue = returnValue;
+		Members = members;
+	}
+}