Polyfill static readonly properties from System.Collections.ObjectModel (#349)

Author: BCSharp

src/core/Microsoft.Dynamic/Microsoft.Dynamic.csproj

@@ -8,7 +8,8 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <EmitCompilerGeneratedFiles>True</EmitCompilerGeneratedFiles>
     <MeziantouPolyfill_IncludedPolyfills>
-      None
+      P:System.Collections.ObjectModel.ReadOnlyCollection`1.Empty;
+      P:System.Collections.ObjectModel.ReadOnlyDictionary`2.Empty;
     </MeziantouPolyfill_IncludedPolyfills>
   </PropertyGroup>
 

src/core/Microsoft.Dynamic/Utils/CollectionExtensions.cs

@@ -127,27 +127,6 @@ internal static T[] RotateRight<T>(this T[] array, int count) {
             Array.Copy(array, sizeOfShiftedArray, result, 0, count);
             return result;
         }
-
-#if !NET8_0_OR_GREATER
-        // Emulates ReadOnlyCollection<T>.Empty form .NET 8.0+ with what is available in .NET Framework et al.
-        // See also polyfill in Microsoft.Scripting.Utils.CollectionExtensions
-        extension<T>(ReadOnlyCollection<T>) {
-            internal static ReadOnlyCollection<T> Empty => EmptyReadOnlyCollection<T>.Instance;
-        }
-
-        private static class EmptyReadOnlyCollection<T> {
-            internal static readonly ReadOnlyCollection<T> Instance = new(Array.Empty<T>());
-        }
-
-        // Emulates ReadOnlyDictionary<TKey,TValue>.Empty from .NET 8.0+ with what is available in .NET Framework et al.
-        extension<TKey, TValue>(ReadOnlyDictionary<TKey, TValue>) {
-            internal static ReadOnlyDictionary<TKey, TValue> Empty => EmptyReadOnlyDictionary<TKey, TValue>.Instance;
-        }
-
-        private static class EmptyReadOnlyDictionary<TKey, TValue> {
-            internal static readonly ReadOnlyDictionary<TKey, TValue> Instance = new(new Dictionary<TKey, TValue>());
-        }
-#endif
     }
 
     internal static class EmptyArray<T> {

src/core/Microsoft.Scripting/Microsoft.Scripting.csproj

@@ -6,7 +6,7 @@
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <EmitCompilerGeneratedFiles>True</EmitCompilerGeneratedFiles>
     <MeziantouPolyfill_IncludedPolyfills>
-      None
+      P:System.Collections.ObjectModel.ReadOnlyCollection`1.Empty;
     </MeziantouPolyfill_IncludedPolyfills>
   </PropertyGroup>
 

src/core/Microsoft.Scripting/Utils/CollectionExtensions.cs

@@ -32,19 +32,5 @@ internal static ReadOnlyCollection<T> ToReadOnlyCollection<T>(this IEnumerable<T
                 },
             };
         }
-
-
-#if !NET8_0_OR_GREATER
-        // Emulates ReadOnlyCollection<T>.Empty form .NET 8.0+ with what is available in .NET Framework et al.
-        extension<T>(ReadOnlyCollection<T>) {
-            internal static ReadOnlyCollection<T> Empty => EmptyReadOnlyCollection<T>.Instance;
-        }
-
-        // CS9282: Extension declarations can include only methods or properties
-        // so a readonly field must be in a separate static class.
-        private static class EmptyReadOnlyCollection<T> {
-            internal static readonly ReadOnlyCollection<T> Instance = new(Array.Empty<T>());
-        }
-#endif
     }
 }