Nullable: Attributes, SafeHandles, and misc (#23810)

* Nullable: Attributes, SafeHandles, and misc

* Address PR feedback

12 files changed, 14 insertions, 2 deletions

diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/CriticalHandleMinusOneIsInvalid.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/CriticalHandleMinusOneIsInvalid.cs
index a76c51d966..8576dacc3d 100644
--- a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/CriticalHandleMinusOneIsInvalid.cs
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/CriticalHandleMinusOneIsInvalid.cs
@@ -2,6 +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.
 
+#nullable enable
 using System;
 using System.Runtime.InteropServices;
 
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/CriticalHandleZeroOrMinusOneIsInvalid.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/CriticalHandleZeroOrMinusOneIsInvalid.cs
index 28d0219489..2b61f6248a 100644
--- a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/CriticalHandleZeroOrMinusOneIsInvalid.cs
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/CriticalHandleZeroOrMinusOneIsInvalid.cs
@@ -2,6 +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.
 
+#nullable enable
 using System;
 using System.Runtime.InteropServices;
 
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFileHandle.Unix.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFileHandle.Unix.cs
index 3b5347dba3..ec99cbf17e 100644
--- a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFileHandle.Unix.cs
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFileHandle.Unix.cs
@@ -2,6 +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.
 
+#nullable enable
 using System;
 using System.Diagnostics;
 using System.IO;
@@ -52,7 +53,7 @@ namespace Microsoft.Win32.SafeHandles
 
                 bool isDirectory = (error.Error == Interop.Error.ENOENT) &&
                     ((flags & Interop.Sys.OpenFlags.O_CREAT) != 0
-                    || !DirectoryExists(Path.GetDirectoryName(PathInternal.TrimEndingDirectorySeparator(path))));
+                    || !DirectoryExists(Path.GetDirectoryName(PathInternal.TrimEndingDirectorySeparator(path!))!));
 
                 Interop.CheckIo(
                     error.Error,
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs
index 4eabe8f08c..db8482ed71 100644
--- a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs
@@ -2,6 +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.
 
+#nullable enable
 using System;
 using System.Security;
 using System.Runtime.InteropServices;
@@ -39,7 +40,7 @@ namespace Microsoft.Win32.SafeHandles
             }
         }
 
-        internal ThreadPoolBoundHandle ThreadPoolBinding { get; set; }
+        internal ThreadPoolBoundHandle? ThreadPoolBinding { get; set; }
 
         override protected bool ReleaseHandle()
         {
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFindHandle.Windows.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFindHandle.Windows.cs
index 4ba05409fd..192f523ff1 100644
--- a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFindHandle.Windows.cs
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFindHandle.Windows.cs
@@ -2,6 +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.
 
+#nullable enable
 using System;
 using System.Security;
 using System.Runtime.InteropServices;
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeHandleMinusOneIsInvalid.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeHandleMinusOneIsInvalid.cs
index 5415f2c35d..b146b5a687 100644
--- a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeHandleMinusOneIsInvalid.cs
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeHandleMinusOneIsInvalid.cs
@@ -2,6 +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.
 
+#nullable enable
 using System;
 using System.Runtime.InteropServices;
 
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeHandleZeroOrMinusOneIsInvalid.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeHandleZeroOrMinusOneIsInvalid.cs
index 8d0220bf90..9a58aa29fe 100644
--- a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeHandleZeroOrMinusOneIsInvalid.cs
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeHandleZeroOrMinusOneIsInvalid.cs
@@ -2,6 +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.
 
+#nullable enable
 using System;
 using System.Runtime.InteropServices;
 
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeLibraryHandle.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeLibraryHandle.cs
index 3be2e354ab..dea7978ee8 100644
--- a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeLibraryHandle.cs
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeLibraryHandle.cs
@@ -2,6 +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.
 
+#nullable enable
 namespace Microsoft.Win32.SafeHandles
 {
     sealed internal class SafeLibraryHandle : SafeHandleZeroOrMinusOneIsInvalid
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeRegistryHandle.Windows.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeRegistryHandle.Windows.cs
index 249f5e9f7c..011aaeae66 100644
--- a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeRegistryHandle.Windows.cs
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeRegistryHandle.Windows.cs
@@ -2,6 +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.
 
+#nullable enable
 using Microsoft.Win32.SafeHandles;
 using System.Runtime.InteropServices;
 
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeRegistryHandle.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeRegistryHandle.cs
index 37e350031b..c3a7fcad88 100644
--- a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeRegistryHandle.cs
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeRegistryHandle.cs
@@ -2,6 +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.
 
+#nullable enable
 using Microsoft.Win32.SafeHandles;
 using System;
 
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeWaitHandle.Windows.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeWaitHandle.Windows.cs
index 66f17f0af7..e87fedd724 100644
--- a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeWaitHandle.Windows.cs
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeWaitHandle.Windows.cs
@@ -2,6 +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.
 
+#nullable enable
 namespace Microsoft.Win32.SafeHandles
 {
     public sealed partial class SafeWaitHandle : SafeHandleZeroOrMinusOneIsInvalid
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeWaitHandle.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeWaitHandle.cs
index edb0cdfcaf..f2e81eacd8 100644
--- a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeWaitHandle.cs
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeWaitHandle.cs
@@ -2,6 +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.
 
+#nullable enable
 using System;
 
 namespace Microsoft.Win32.SafeHandles