Resolve SDK 8.0.2xx diagnostics (#2100)

It looks like the 8.0.200 .NET SDK added a lot of new diagnostics suggesting the use of collection expressions.

For the most part we have taken these suggestions, but in some cases we've retained the existing code so you can see what types are being used. I find that in methods with lots of overloads (e.g., Assert.AreEqual) it becomes quite difficult to work out what will actually happen if you replace an explicitly typed list initializer with just `[...]`.

Author: idg10

Ix.NET/Integration/Android/Resources/Resource.Designer.cs

@@ -9,7 +9,7 @@
     <Description>Reactive Extensions (Rx) for .NET - Testing Library</Description>
     <PackageReadmeFile>readme.md</PackageReadmeFile>
     <!-- NB: A lot of CA and IDE warnings are disabled because of the .cs files included from xunit.assert.source. -->
-    <NoWarn>$(NoWarn);IDE0054;IDE0066;CA1305;CA1307;CA1032;CA1064;CA1704;CA1822;CA1812;CA1820;CA1823;CA1825;CA1845;CA2249;IDE0016;IDE0018;IDE0019;IDE0020;IDE0031;IDE0039;IDE0044;IDE0059;IDE0074;IDE0270</NoWarn>
+    <NoWarn>$(NoWarn);IDE0054;IDE0066;CA1305;CA1307;CA1032;CA1064;CA1704;CA1822;CA1812;CA1820;CA1823;CA1825;CA1845;CA2249;IDE0016;IDE0018;IDE0019;IDE0020;IDE0028;IDE0031;IDE0039;IDE0044;IDE0059;IDE0074;IDE0090;IDE0270;IDE0300</NoWarn>
   </PropertyGroup>
 
   <PropertyGroup>

Rx.NET/Integration/Installation/Android/Resources/Resource.Designer.cs

@@ -39,7 +39,7 @@ public IEnumerable<E> this[K key]
             {
                 if (!_dictionary.TryGetValue(key, out var list))
                 {
-                    return Enumerable.Empty<E>();
+                    return [];
                 }
 
                 return Hide(list);

Rx.NET/Source/src/Microsoft.Reactive.Testing/Microsoft.Reactive.Testing.csproj

@@ -29,7 +29,7 @@ internal sealed class ExactSink : Sink<TSource, IList<TSource>>
             {
                 private readonly int _count;
                 private int _index;
-                private IList<TSource>? _buffer;
+                private List<TSource>? _buffer;
 
                 internal ExactSink(IObserver<IList<TSource>> observer, int count) : base(observer)
                 {
@@ -41,7 +41,7 @@ public override void OnNext(TSource value)
                     var buffer = _buffer;
                     if (buffer == null)
                     {
-                        buffer = new List<TSource>();
+                        buffer = [];
                         _buffer = buffer;
                     }
 
@@ -102,7 +102,7 @@ internal sealed class SkipSink : Sink<TSource, IList<TSource>>
                 private readonly int _count;
                 private readonly int _skip;
                 private int _index;
-                private IList<TSource>? _buffer;
+                private List<TSource>? _buffer;
 
                 internal SkipSink(IObserver<IList<TSource>> observer, int count, int skip) : base(observer)
                 {
@@ -116,7 +116,7 @@ public override void OnNext(TSource value)
                     var buffer = _buffer;
                     if (idx == 0)
                     {
-                        buffer = new List<TSource>();
+                        buffer = [];
                         _buffer = buffer;
                     }
 

Rx.NET/Source/src/System.Reactive/Internal/Lookup.cs

@@ -135,13 +135,13 @@ public void Dispose()
 
             private Action AddHandlerCore(Delegate handler)
             {
-                _addMethod.Invoke(_target, new object[] { handler });
-                return () => _removeMethod.Invoke(_target, new object[] { handler });
+                _addMethod.Invoke(_target, [handler]);
+                return () => _removeMethod.Invoke(_target, [handler]);
             }
 
             private Action AddHandlerCoreWinRT(Delegate handler)
             {
-                var token = _addMethod.Invoke(_target, new object[] { handler });
+                var token = _addMethod.Invoke(_target, [handler]);
                 return () => _removeMethod.Invoke(_target, [token]);
             }
         }

Rx.NET/Source/src/System.Reactive/Linq/Observable/Buffer.cs

@@ -16,7 +16,7 @@ internal partial class QueryLanguage
 
         public virtual IEnumerable<IList<TSource>> Chunkify<TSource>(IObservable<TSource> source)
         {
-            return source.Collect<TSource, IList<TSource>>(() => new List<TSource>(), (lst, x) => { lst.Add(x); return lst; }, _ => new List<TSource>());
+            return source.Collect<TSource, IList<TSource>>(() => [], (lst, x) => { lst.Add(x); return lst; }, _ => []);
         }
 
         #endregion

Rx.NET/Source/src/System.Reactive/Linq/Observable/FromEventPattern.cs

@@ -322,13 +322,13 @@ private IList<Expression> VisitQbservableOperatorArguments(MethodInfo method, IE
                     if (lastArgument.NodeType == ExpressionType.NewArrayInit)
                     {
                         var paramsArray = (NewArrayExpression)lastArgument;
-                        return new List<Expression>
-                        {
+                        return
+                        [
                             Expression.NewArrayInit(
                                 typeof(Plan<>).MakeGenericType(method.GetGenericArguments()[0]),
                                 paramsArray.Expressions.Select(param => Visit(param))
                             )
-                        };
+                        ];
                     }
                 }
 

Rx.NET/Source/src/System.Reactive/Linq/QueryLanguage.Blocking.cs

@@ -22,7 +22,7 @@ public sealed class AsyncSubject<T> : SubjectBase<T>, INotifyCompletion
         private bool _hasValue;
         private Exception? _exception;
 
-#pragma warning disable CA1825 // (Avoid zero-length array allocations.) The identity of these arrays matters, so we can't use the shared Array.Empty<T>() instance
+#pragma warning disable CA1825,IDE0300 // (Avoid zero-length array allocations. Use collection expressions) The identity of these arrays matters, so we can't use the shared Array.Empty<T>() instance either explicitly, or indirectly via a collection expression
         /// <summary>
         /// A pre-allocated empty array indicating the AsyncSubject has terminated.
         /// </summary>
@@ -31,7 +31,7 @@ public sealed class AsyncSubject<T> : SubjectBase<T>, INotifyCompletion
         /// A pre-allocated empty array indicating the AsyncSubject has been disposed.
         /// </summary>
         private static readonly AsyncSubjectDisposable[] Disposed = new AsyncSubjectDisposable[0];
-#pragma warning restore CA1825
+#pragma warning restore CA1825,IDE0300
 
         #endregion
 

Rx.NET/Source/src/System.Reactive/ObservableQuery.cs

@@ -18,10 +18,10 @@ public sealed class Subject<T> : SubjectBase<T>
 
         private SubjectDisposable[] _observers;
         private Exception? _exception;
-#pragma warning disable CA1825 // (Avoid zero-length array allocations.) The identity of these arrays matters, so we can't use the shared Array.Empty<T>() instance
+#pragma warning disable CA1825,IDE0300 // (Avoid zero-length array allocations. Use collection expressions) The identity of these arrays matters, so we can't use the shared Array.Empty<T>() instance either explicitly, or indirectly via a collection expression
         private static readonly SubjectDisposable[] Terminated = new SubjectDisposable[0];
         private static readonly SubjectDisposable[] Disposed = new SubjectDisposable[0];
-#pragma warning restore CA1825
+#pragma warning restore CA1825,IDE0300
 
         #endregion