dotnet · stephentoub · Sep 19, 2017 · Sep 9, 2017 · Sep 11, 2017 · Sep 11, 2017
diff --git a/src/System.Memory/ref/System.Memory.cs b/src/System.Memory/ref/System.Memory.cs
@@ -7,7 +7,7 @@
 
 namespace System
 {
-    public struct ReadOnlySpan<T>
+    public readonly ref struct ReadOnlySpan<T>
     {
         public static ReadOnlySpan<T> Empty { get { throw null; } }
         public ReadOnlySpan(T[] array) { throw null;}
@@ -39,7 +39,7 @@ public void CopyTo(Span<T> destination) { }
         public bool TryCopyTo(Span<T> destination) { throw null; }
     }
 
-    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/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
@@ -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.Memory/src/System/ReadOnlySpan.cs b/src/System.Memory/src/System/ReadOnlySpan.cs
@@ -15,7 +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>
-    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
@@ -17,7 +17,7 @@ namespace System
     /// </summary>
     [DebuggerTypeProxy(typeof(SpanDebugView<>))]
     [DebuggerDisplay("Length = {Length}")]
-    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
@@ -1881,7 +1881,7 @@ public struct ReadOnlyMemory<T>
         public bool DangerousTryGetArray(out ArraySegment<T> arraySegment) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    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; }
@@ -2068,7 +2068,7 @@ 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)]
-    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; }

diff --git 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'" />