More auto-fixing of corelib (primarily mono/netcore) (#34071)

* Use explicit type

* Use pattern matching

* Use null propagation

* Simplify default expressions

* Order modifiers

* Simplify null checks

* Make fields readonly

* Delete dead members

* Use switch expressions

* Remove unnecessary usings

* Fix a few issues

src/libraries/Common/src/Interop/Unix/Interop.Errors.cs

@@ -115,7 +115,7 @@ internal enum Error
     // Represents a platform-agnostic Error and underlying platform-specific errno
     internal struct ErrorInfo
     {
-        private Error _error;
+        private readonly Error _error;
         private int _rawErrno;
 
         internal ErrorInfo(int errno)

src/libraries/Common/src/Interop/Unix/System.Globalization.Native/Interop.Calendar.cs

@@ -5,7 +5,6 @@
 using System;
 using System.Globalization;
 using System.Runtime.InteropServices;
-using System.Text;
 
 internal static partial class Interop
 {

src/libraries/Common/src/Interop/Unix/System.Globalization.Native/Interop.Casing.cs

@@ -2,10 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Runtime.InteropServices;
-using System.Security;
-using System.Text;
 
 internal static partial class Interop
 {

src/libraries/Common/src/Interop/Unix/System.Globalization.Native/Interop.Collation.cs

@@ -5,7 +5,6 @@
 using System;
 using System.Globalization;
 using System.Runtime.InteropServices;
-using System.Security;
 
 internal static partial class Interop
 {

src/libraries/Common/src/Interop/Unix/System.Globalization.Native/Interop.ICU.cs

@@ -2,9 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Runtime.InteropServices;
-using System.Runtime.CompilerServices;
 
 internal static partial class Interop
 {

src/libraries/Common/src/Interop/Unix/System.Globalization.Native/Interop.Idna.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop

src/libraries/Common/src/Interop/Unix/System.Globalization.Native/Interop.Locale.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop

src/libraries/Common/src/Interop/Unix/System.Globalization.Native/Interop.Normalization.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Runtime.InteropServices;
 using System.Text;
 

src/libraries/Common/src/Interop/Unix/System.Globalization.Native/Interop.TimeZoneInfo.cs

@@ -3,7 +3,6 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Runtime.InteropServices;
-using System.Text;
 
 internal static partial class Interop
 {

src/libraries/Common/src/Interop/Unix/System.Globalization.Native/Interop.Utils.cs

@@ -3,9 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
-using System.Diagnostics;
 using System.Buffers;
-using System.Text;
 
 internal static partial class Interop
 {

src/libraries/Common/src/Interop/Unix/System.Native/Interop.Access.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop

src/libraries/Common/src/Interop/Unix/System.Native/Interop.ChDir.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop

src/libraries/Common/src/Interop/Unix/System.Native/Interop.GetCpuUtilization.cs

@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop

src/libraries/Common/src/Interop/Unix/System.Native/Interop.GetEUid.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop

src/libraries/Common/src/Interop/Unix/System.Native/Interop.GetPid.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop

src/libraries/Common/src/Interop/Unix/System.Native/Interop.GetPwUid.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop

src/libraries/Common/src/Interop/Unix/System.Native/Interop.GetRandomBytes.cs

@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.Diagnostics;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop

src/libraries/Common/src/Interop/Unix/System.Native/Interop.LockFileRegion.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop

src/libraries/Common/src/Interop/Unix/System.Native/Interop.MountPoints.cs

@@ -3,7 +3,6 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
-using System.Collections.Generic;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop

src/libraries/Common/src/Interop/Unix/System.Native/Interop.PathConf.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop

src/libraries/Common/src/Interop/Unix/System.Native/Interop.Read.cs

@@ -3,7 +3,6 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Runtime.InteropServices;
-using Microsoft.Win32.SafeHandles;
 
 internal static partial class Interop
 {

src/libraries/Common/src/Interop/Unix/System.Native/Interop.Write.cs

@@ -3,7 +3,6 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Runtime.InteropServices;
-using Microsoft.Win32.SafeHandles;
 
 internal static partial class Interop
 {

src/libraries/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeFileHandle.Unix.cs

@@ -5,7 +5,6 @@
 using System;
 using System.Diagnostics;
 using System.IO;
-using System.Runtime.InteropServices;
 
 namespace Microsoft.Win32.SafeHandles
 {

src/libraries/System.Private.CoreLib/src/System/Collections/Generic/ISet.cs

@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Runtime.CompilerServices;
-
 namespace System.Collections.Generic
 {
     /// <summary>

src/libraries/System.Private.CoreLib/src/System/Diagnostics/DebugProvider.Unix.cs

@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using Microsoft.Win32.SafeHandles;
-
 namespace System.Diagnostics
 {
     public partial class DebugProvider

src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventPipe.cs

@@ -1,8 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
+
 using System.Collections.Generic;
-using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Threading;
 

src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/RuntimeEventSourceHelper.Unix.cs

@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-
 namespace System.Diagnostics.Tracing
 {
     internal static class RuntimeEventSourceHelper

src/libraries/System.Private.CoreLib/src/System/Environment.NoRegistry.cs

@@ -2,9 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Diagnostics;
 using System.Collections;
-using Microsoft.Win32;
 
 namespace System
 {

src/libraries/System.Private.CoreLib/src/System/Environment.Unix.cs

@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Collections;
-using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
 using System.Reflection;
@@ -454,8 +452,8 @@ public static long WorkingSet
                 {
                     using (currentProcess)
                     {
-                        object? result = processType!.GetMethod("get_WorkingSet64")?.Invoke(currentProcess, BindingFlags.DoNotWrapExceptions, null, null, null);
-                        if (result is long) return (long)result;
+                        if (processType!.GetMethod("get_WorkingSet64")?.Invoke(currentProcess, BindingFlags.DoNotWrapExceptions, null, null, null) is long result)
+                            return result;
                     }
                 }
 

src/libraries/System.Private.CoreLib/src/System/Globalization/CalendarData.Unix.cs

@@ -4,7 +4,6 @@
 
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Security;
 using System.Text;
 using Internal.Runtime.CompilerServices;
 

src/libraries/System.Private.CoreLib/src/System/Globalization/CompareInfo.Unix.cs

@@ -5,12 +5,7 @@
 using System.Buffers;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-using System.Security;
-using System.Threading;
-
-using Internal.Runtime.CompilerServices;
 
 namespace System.Globalization
 {

src/libraries/System.Private.CoreLib/src/System/Globalization/CultureData.Unix.cs

@@ -2,12 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Runtime.InteropServices;
-using System.Security;
-using System.Text;
 
 namespace System.Globalization
 {

src/libraries/System.Private.CoreLib/src/System/Globalization/JapaneseCalendar.Unix.cs

@@ -74,7 +74,7 @@ private static bool GetJapaneseEraStartDate(int era, out DateTime dateTime)
         {
             Debug.Assert(!GlobalizationMode.Invariant);
 
-            dateTime = default(DateTime);
+            dateTime = default;
 
             int startYear;
             int startMonth;

src/libraries/System.Private.CoreLib/src/System/Globalization/TextInfo.Unix.cs

@@ -3,9 +3,6 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Diagnostics;
-using System.Runtime.InteropServices;
-using System.Security;
-using System.Text;
 
 namespace System.Globalization
 {

src/libraries/System.Private.CoreLib/src/System/Guid.Unix.cs

@@ -2,9 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Diagnostics;
-using System.Runtime.InteropServices;
-
 namespace System
 {
     public partial struct Guid

src/libraries/System.Private.CoreLib/src/System/IO/BufferedStream.cs

@@ -672,7 +672,7 @@ public override Task<int> ReadAsync(byte[] buffer, int offset, int count, Cancel
                 cancellationToken, bytesFromBuffer, semaphoreLockTask).AsTask();
         }
 
-        public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken))
+        public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default)
         {
             if (cancellationToken.IsCancellationRequested)
             {
@@ -837,19 +837,6 @@ private int WriteToBuffer(ReadOnlySpan<byte> buffer)
             return bytesToWrite;
         }
 
-        private void WriteToBuffer(byte[] array, ref int offset, ref int count, out Exception? error)
-        {
-            try
-            {
-                error = null;
-                WriteToBuffer(array, ref offset, ref count);
-            }
-            catch (Exception ex)
-            {
-                error = ex;
-            }
-        }
-
         public override void Write(byte[] array, int offset, int count)
         {
             if (array == null)
@@ -1074,7 +1061,7 @@ public override Task WriteAsync(byte[] buffer, int offset, int count, Cancellati
             return WriteAsync(new ReadOnlyMemory<byte>(buffer, offset, count), cancellationToken).AsTask();
         }
 
-        public override ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken))
+        public override ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken cancellationToken = default)
         {
             // Fast path check for cancellation already requested
             if (cancellationToken.IsCancellationRequested)

src/libraries/System.Private.CoreLib/src/System/IO/DriveInfoInternal.Unix.cs

@@ -2,9 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Diagnostics;
-using System.Text;
-
 namespace System.IO
 {
     /// <summary>Contains internal volume helpers that are shared between many projects.</summary>

src/libraries/System.Private.CoreLib/src/System/IO/FileAttributes.cs

@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-
 namespace System.IO
 {
     [Flags]

src/libraries/System.Private.CoreLib/src/System/IO/FileStream.Linux.cs

@@ -2,11 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using Microsoft.Win32.SafeHandles;
-using System.Diagnostics;
-using System.Threading;
-using System.Threading.Tasks;
-
 namespace System.IO
 {
     public partial class FileStream : Stream