From 90ab57c5626df29fbb58e53612defac02833eb8a Mon Sep 17 00:00:00 2001
From: Julien Couvreur <jcouv@users.noreply.github.com>
Date: Thu, 19 Mar 2020 11:31:17 -0700
Subject: [PATCH] Add MemberNotNull/When attributes (#33567)

* Add MemberNotNull/When attributes

* Apply [CLSCompliant(false)]

* Fix typos and indent

* Move [CLSCompliant(false)] and remove AllowMultiple

* Declare attributes in ref file

* Store parameters into readonly properties

* Don't use deconstruction

* Qualify, move properties, remove this
---
 .../Diagnostics/CodeAnalysis/NullableAttributes.cs | 51 ++++++++++++++++++++++
 src/libraries/System.Runtime/ref/System.Runtime.cs | 15 +++++++
 2 files changed, 66 insertions(+)

diff --git a/src/libraries/System.Private.CoreLib/src/System/Diagnostics/CodeAnalysis/NullableAttributes.cs b/src/libraries/System.Private.CoreLib/src/System/Diagnostics/CodeAnalysis/NullableAttributes.cs
index 0b24c01..35a5948 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Diagnostics/CodeAnalysis/NullableAttributes.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Diagnostics/CodeAnalysis/NullableAttributes.cs
@@ -125,4 +125,55 @@ namespace System.Diagnostics.CodeAnalysis
         /// <summary>Gets the condition parameter value.</summary>
         public bool ParameterValue { get; }
     }
+
+    /// <summary>Specifies that the method or property will ensure that the listed field and property members have not-null values.</summary>
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Property, Inherited = false)]
+#if INTERNAL_NULLABLE_ATTRIBUTES
+    internal
+#else
+    [CLSCompliant(false)]
+    public
+#endif
+        sealed class MemberNotNullAttribute : Attribute
+    {
+        /// <summary>Initializes the attribute with the list of field and property members.</summary>
+        /// <param name="members">
+        /// The list of field and property members that are promised to be not-null.
+        /// </param>
+        public MemberNotNullAttribute(params string[] members)
+            => Members = members;
+
+        /// <summary>Gets field or property member names.</summary>
+        public string[] Members { get; }
+    }
+
+    /// <summary>Specifies that the method or property will ensure that the listed field and property members have not-null values when returning with the specified return value condition.</summary>
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Property, Inherited = false)]
+#if INTERNAL_NULLABLE_ATTRIBUTES
+    internal
+#else
+    [CLSCompliant(false)]
+    public
+#endif
+        sealed class MemberNotNullWhenAttribute : Attribute
+    {
+        /// <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>
+        public MemberNotNullWhenAttribute(bool returnValue, params string[] members)
+        {
+            ReturnValue = returnValue;
+            Members = members;
+        }
+
+        /// <summary>Gets the return value condition.</summary>
+        public bool ReturnValue { get; }
+
+        /// <summary>Gets field or property member names.</summary>
+        public string[] Members { get; }
+    }
 }
diff --git a/src/libraries/System.Runtime/ref/System.Runtime.cs b/src/libraries/System.Runtime/ref/System.Runtime.cs
index d09b7e3..4771f24 100644
--- a/src/libraries/System.Runtime/ref/System.Runtime.cs
+++ b/src/libraries/System.Runtime/ref/System.Runtime.cs
@@ -5618,6 +5618,21 @@ namespace System.Diagnostics.CodeAnalysis
         public NotNullWhenAttribute(bool returnValue) { }
         public bool ReturnValue { get { throw null; } }
     }
+    [System.AttributeUsage(System.AttributeTargets.Method | System.AttributeTargets.Property, Inherited = false)]
+    [System.CLSCompliant(false)]
+    public sealed class MemberNotNullAttribute : System.Attribute
+    {
+        public MemberNotNullAttribute(params string[] members) { }
+        public string[] Members { get { throw null; } }
+    }
+    [System.AttributeUsage(System.AttributeTargets.Method | System.AttributeTargets.Property, Inherited = false)]
+    [System.CLSCompliant(false)]
+    public sealed class MemberNotNullWhenAttribute : System.Attribute
+    {
+        public MemberNotNullWhenAttribute(bool returnValue, params string[] members) { }
+        public bool ReturnValue { get { throw null; } }
+        public string[] Members { get { throw null; } }
+    }
     [System.AttributeUsageAttribute(System.AttributeTargets.All, Inherited=false, AllowMultiple=true)]
     [System.Diagnostics.ConditionalAttribute("CODE_ANALYSIS")]
     public sealed partial class SuppressMessageAttribute : System.Attribute
-- 
2.7.4