From c5f7390d4317fe4f9599fda56c1d6d91a69fe29b Mon Sep 17 00:00:00 2001
From: ahsonkhan <ahson_ahmedk@yahoo.com>
Date: Fri, 8 Sep 2017 22:18:50 -0700
Subject: [PATCH 1/4] Marking {ReadOnly}Span as readonly structs, fixing issue
 #23809

---
 src/System.Memory/src/System/ReadOnlySpan.cs | 2 ++
 src/System.Memory/src/System/Span.cs         | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/src/System.Memory/src/System/ReadOnlySpan.cs b/src/System.Memory/src/System/ReadOnlySpan.cs
index cfd4f56d71cc..9871645fe22d 100644
--- a/src/System.Memory/src/System/ReadOnlySpan.cs
+++ b/src/System.Memory/src/System/ReadOnlySpan.cs
@@ -15,6 +15,8 @@ namespace System
     /// ReadOnlySpan represents a contiguous region of arbitrary memory. Unlike arrays, it can point to either managed
     /// or native memory, or to memory allocated on the stack. It is type- and memory-safe.
     /// </summary>
+    [IsReadOnly]
+    [IsByRefLike]
     public struct ReadOnlySpan<T>
     {
         /// <summary>
diff --git a/src/System.Memory/src/System/Span.cs b/src/System.Memory/src/System/Span.cs
index 02609491939f..b805d4515ddb 100644
--- a/src/System.Memory/src/System/Span.cs
+++ b/src/System.Memory/src/System/Span.cs
@@ -17,6 +17,8 @@ namespace System
     /// </summary>
     [DebuggerTypeProxy(typeof(SpanDebugView<>))]
     [DebuggerDisplay("Length = {Length}")]
+    [IsReadOnly]
+    [IsByRefLike]
     public struct Span<T>
     {
         /// <summary>

From 1197c3cf3259363d05e90dea7ba1d2d8edbdc485 Mon Sep 17 00:00:00 2001
From: ahsonkhan <ahson_ahmedk@yahoo.com>
Date: Mon, 11 Sep 2017 14:03:17 -0700
Subject: [PATCH 2/4] Adding readonly attributes to reference assemblies.

---
 src/System.Memory/ref/System.Memory.cs   | 4 ++++
 src/System.Runtime/ref/System.Runtime.cs | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/src/System.Memory/ref/System.Memory.cs b/src/System.Memory/ref/System.Memory.cs
index dd7ceb0b2c97..912d4b5db357 100644
--- a/src/System.Memory/ref/System.Memory.cs
+++ b/src/System.Memory/ref/System.Memory.cs
@@ -8,6 +8,8 @@
 #pragma warning disable 0809  //warning CS0809: Obsolete member 'Span<T>.Equals(object)' overrides non-obsolete member 'object.Equals(object)'
 namespace System
 {
+    [System.Runtime.CompilerServices.IsReadOnly]
+    [System.Runtime.CompilerServices.IsByRefLike]
     public struct ReadOnlySpan<T>
     {
         public static ReadOnlySpan<T> Empty { get { throw null; } }
@@ -36,6 +38,8 @@ public void CopyTo(Span<T> destination) { }
         public bool TryCopyTo(Span<T> destination) { throw null; }
     }
 
+    [System.Runtime.CompilerServices.IsReadOnly]
+    [System.Runtime.CompilerServices.IsByRefLike]
     public struct Span<T>
     {
         public static Span<T> Empty { get { throw null; } }
diff --git a/src/System.Runtime/ref/System.Runtime.cs b/src/System.Runtime/ref/System.Runtime.cs
index 12f1f7873696..fa796df4d798 100644
--- a/src/System.Runtime/ref/System.Runtime.cs
+++ b/src/System.Runtime/ref/System.Runtime.cs
@@ -1832,6 +1832,8 @@ public RankException(string message, System.Exception innerException) { }
         protected RankException(System.Runtime.Serialization.SerializationInfo info, System.Runtime.Serialization.StreamingContext context) : base(info, context) { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
+    [System.Runtime.CompilerServices.IsReadOnly]
+    [System.Runtime.CompilerServices.IsByRefLike]
     public partial struct ReadOnlySpan<T>
     {
         public static ReadOnlySpan<T> Empty { get { throw null; } }
@@ -2017,6 +2019,8 @@ public partial struct Single : System.IComparable, System.IComparable<float>, Sy
         public static bool TryParse(ReadOnlySpan<char> s, out float result, System.Globalization.NumberStyles style = System.Globalization.NumberStyles.Integer, System.IFormatProvider provider = null) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
+    [System.Runtime.CompilerServices.IsReadOnly]
+    [System.Runtime.CompilerServices.IsByRefLike]
     public partial struct Span<T>
     {
         public static Span<T> Empty { get { throw null; } }

From 14add503537edbc9e865d54ecd6abad938a1bbe7 Mon Sep 17 00:00:00 2001
From: ahsonkhan <ahson_ahmedk@yahoo.com>
Date: Mon, 11 Sep 2017 15:58:21 -0700
Subject: [PATCH 3/4] Using "readonly ref" keyword instead of attributes.

---
 src/System.Memory/ref/System.Memory.cs       | 8 ++------
 src/System.Memory/src/System/ReadOnlySpan.cs | 4 +---
 src/System.Memory/src/System/Span.cs         | 4 +---
 src/System.Runtime/ref/System.Runtime.cs     | 8 ++------
 4 files changed, 6 insertions(+), 18 deletions(-)

diff --git a/src/System.Memory/ref/System.Memory.cs b/src/System.Memory/ref/System.Memory.cs
index 912d4b5db357..d5430348c0c3 100644
--- a/src/System.Memory/ref/System.Memory.cs
+++ b/src/System.Memory/ref/System.Memory.cs
@@ -8,9 +8,7 @@
 #pragma warning disable 0809  //warning CS0809: Obsolete member 'Span<T>.Equals(object)' overrides non-obsolete member 'object.Equals(object)'
 namespace System
 {
-    [System.Runtime.CompilerServices.IsReadOnly]
-    [System.Runtime.CompilerServices.IsByRefLike]
-    public struct ReadOnlySpan<T>
+    public readonly ref struct ReadOnlySpan<T>
     {
         public static ReadOnlySpan<T> Empty { get { throw null; } }
         public ReadOnlySpan(T[] array) { throw null;}
@@ -38,9 +36,7 @@ public void CopyTo(Span<T> destination) { }
         public bool TryCopyTo(Span<T> destination) { throw null; }
     }
 
-    [System.Runtime.CompilerServices.IsReadOnly]
-    [System.Runtime.CompilerServices.IsByRefLike]
-    public struct Span<T>
+    public readonly ref struct Span<T>
     {
         public static Span<T> Empty { get { throw null; } }
         public Span(T[] array) { throw null;}
diff --git a/src/System.Memory/src/System/ReadOnlySpan.cs b/src/System.Memory/src/System/ReadOnlySpan.cs
index 9871645fe22d..72346d490168 100644
--- a/src/System.Memory/src/System/ReadOnlySpan.cs
+++ b/src/System.Memory/src/System/ReadOnlySpan.cs
@@ -15,9 +15,7 @@ namespace System
     /// ReadOnlySpan represents a contiguous region of arbitrary memory. Unlike arrays, it can point to either managed
     /// or native memory, or to memory allocated on the stack. It is type- and memory-safe.
     /// </summary>
-    [IsReadOnly]
-    [IsByRefLike]
-    public struct ReadOnlySpan<T>
+    public readonly ref struct ReadOnlySpan<T>
     {
         /// <summary>
         /// Creates a new read-only span over the entirety of the target array.
diff --git a/src/System.Memory/src/System/Span.cs b/src/System.Memory/src/System/Span.cs
index b805d4515ddb..65b313dd6c27 100644
--- a/src/System.Memory/src/System/Span.cs
+++ b/src/System.Memory/src/System/Span.cs
@@ -17,9 +17,7 @@ namespace System
     /// </summary>
     [DebuggerTypeProxy(typeof(SpanDebugView<>))]
     [DebuggerDisplay("Length = {Length}")]
-    [IsReadOnly]
-    [IsByRefLike]
-    public struct Span<T>
+    public readonly ref struct Span<T>
     {
         /// <summary>
         /// Creates a new span over the entirety of the target array.
diff --git a/src/System.Runtime/ref/System.Runtime.cs b/src/System.Runtime/ref/System.Runtime.cs
index fa796df4d798..0259c61049e1 100644
--- a/src/System.Runtime/ref/System.Runtime.cs
+++ b/src/System.Runtime/ref/System.Runtime.cs
@@ -1832,9 +1832,7 @@ public RankException(string message, System.Exception innerException) { }
         protected RankException(System.Runtime.Serialization.SerializationInfo info, System.Runtime.Serialization.StreamingContext context) : base(info, context) { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    [System.Runtime.CompilerServices.IsReadOnly]
-    [System.Runtime.CompilerServices.IsByRefLike]
-    public partial struct ReadOnlySpan<T>
+    public readonly ref struct ReadOnlySpan<T>
     {
         public static ReadOnlySpan<T> Empty { get { throw null; } }
         public ReadOnlySpan(T[] array) { throw null; }
@@ -2019,9 +2017,7 @@ public partial struct Single : System.IComparable, System.IComparable<float>, Sy
         public static bool TryParse(ReadOnlySpan<char> s, out float result, System.Globalization.NumberStyles style = System.Globalization.NumberStyles.Integer, System.IFormatProvider provider = null) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    [System.Runtime.CompilerServices.IsReadOnly]
-    [System.Runtime.CompilerServices.IsByRefLike]
-    public partial struct Span<T>
+    public readonly ref struct Span<T>
     {
         public static Span<T> Empty { get { throw null; } }
         public Span(T[] array) { throw null; }

From cbbbe1d67d784620f24848dd243c93b0d80a4b71 Mon Sep 17 00:00:00 2001
From: ahsonkhan <ahson_ahmedk@yahoo.com>
Date: Mon, 18 Sep 2017 20:14:07 -0700
Subject: [PATCH 4/4] Adding a LangVersion 7.2 property

---
 src/System.Memory/ref/System.Memory.csproj   | 1 +
 src/System.Memory/src/System.Memory.csproj   | 1 +
 src/System.Runtime/ref/System.Runtime.csproj | 1 +
 3 files changed, 3 insertions(+)

diff --git a/src/System.Memory/ref/System.Memory.csproj b/src/System.Memory/ref/System.Memory.csproj
index 0d0db9a2fd95..6226292ea1aa 100644
--- a/src/System.Memory/ref/System.Memory.csproj
+++ b/src/System.Memory/ref/System.Memory.csproj
@@ -6,6 +6,7 @@
     <CLSCompliant>false</CLSCompliant>
     <ProjectGuid>{E883935B-D8FD-4FC9-A189-9D9E7F7EF550}</ProjectGuid>
     <IsPartialFacadeAssembly Condition="'$(TargetGroup)' == 'netcoreapp' Or '$(TargetGroup)' == 'uap'">true</IsPartialFacadeAssembly>
+    <LangVersion>7.2</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'netstandard-Debug|AnyCPU'" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'netstandard-Release|AnyCPU'" />
diff --git a/src/System.Memory/src/System.Memory.csproj b/src/System.Memory/src/System.Memory.csproj
index 1091463c00c4..04eaf96d323e 100644
--- a/src/System.Memory/src/System.Memory.csproj
+++ b/src/System.Memory/src/System.Memory.csproj
@@ -9,6 +9,7 @@
     <IsPartialFacadeAssembly Condition="'$(TargetGroup)' == 'netcoreapp' OR '$(TargetGroup)' == 'uap'">true</IsPartialFacadeAssembly>
     <DefineConstants Condition="'$(TargetGroup)'=='netcoreapp'">$(DefineConstants);netcoreapp</DefineConstants>
     <DefineConstants Condition="'$(TargetGroup)'=='netstandard1.1'">$(DefineConstants);netstandard11</DefineConstants>
+     <LangVersion>7.2</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'netcoreapp-Unix-Debug|AnyCPU'" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'netcoreapp-Unix-Release|AnyCPU'" />
diff --git a/src/System.Runtime/ref/System.Runtime.csproj b/src/System.Runtime/ref/System.Runtime.csproj
index 349f7efa2045..7b13bb87fedf 100644
--- a/src/System.Runtime/ref/System.Runtime.csproj
+++ b/src/System.Runtime/ref/System.Runtime.csproj
@@ -5,6 +5,7 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IsCoreAssembly>true</IsCoreAssembly>
     <ProjectGuid>{ADBCF120-3454-4A3C-9D1D-AC4293E795D6}</ProjectGuid>
+    <LangVersion>7.2</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'netcoreapp-Debug|AnyCPU'" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'netcoreapp-Release|AnyCPU'" />