Update Net5Compat impl as well

Author: stephentoub

src/libraries/System.Private.CoreLib/src/System/IO/Strategies/Net5CompatFileStreamStrategy.Unix.cs

@@ -108,7 +108,7 @@ protected override void Dispose(bool disposing)
 
                         if (SafeFileHandle.t_lastCloseErrorInfo != null)
                         {
-                            throw Interop.GetExceptionForIoErrno(SafeFileHandle.t_lastCloseErrorInfo.GetValueOrDefault(), _path, isDirectory: false);
+                            throw Interop.GetExceptionForIoErrno(SafeFileHandle.t_lastCloseErrorInfo.GetValueOrDefault(), _fileHandle.Path, isDirectory: false);
                         }
                     }
                 }
@@ -156,7 +156,7 @@ private void FlushOSBuffer()
                         // doesn't support synchronization.  In such cases there's nothing to flush.
                         break;
                     default:
-                        throw Interop.GetExceptionForIoErrno(errorInfo, _path, isDirectory: false);
+                        throw Interop.GetExceptionForIoErrno(errorInfo, _fileHandle.Path, isDirectory: false);
                 }
             }
         }
@@ -604,14 +604,14 @@ private long SeekCore(SafeFileHandle fileHandle, long offset, SeekOrigin origin,
             Debug.Assert(fileHandle.CanSeek);
             Debug.Assert(origin >= SeekOrigin.Begin && origin <= SeekOrigin.End);
 
-            long pos = FileStreamHelpers.CheckFileCall(Interop.Sys.LSeek(fileHandle, offset, (Interop.Sys.SeekWhence)(int)origin), _path); // SeekOrigin values are the same as Interop.libc.SeekWhence values
+            long pos = FileStreamHelpers.CheckFileCall(Interop.Sys.LSeek(fileHandle, offset, (Interop.Sys.SeekWhence)(int)origin), fileHandle.Path); // SeekOrigin values are the same as Interop.libc.SeekWhence values
             _filePosition = pos;
             return pos;
         }
 
         private int CheckFileCall(int result, bool ignoreNotSupported = false)
         {
-            FileStreamHelpers.CheckFileCall(result, _path, ignoreNotSupported);
+            FileStreamHelpers.CheckFileCall(result, _fileHandle?.Path, ignoreNotSupported);
 
             return result;
         }

src/libraries/System.Private.CoreLib/src/System/IO/Strategies/Net5CompatFileStreamStrategy.Windows.cs

@@ -374,7 +374,7 @@ private unsafe int ReadNative(Span<byte> buffer)
                     if (errorCode == Interop.Errors.ERROR_INVALID_PARAMETER)
                         ThrowHelper.ThrowArgumentException_HandleNotSync(nameof(_fileHandle));
 
-                    throw Win32Marshal.GetExceptionForWin32Error(errorCode, _path);
+                    throw Win32Marshal.GetExceptionForWin32Error(errorCode, _fileHandle.Path);
                 }
             }
             Debug.Assert(r >= 0, "FileStream's ReadNative is likely broken.");
@@ -578,7 +578,7 @@ private unsafe void WriteCore(ReadOnlySpan<byte> source)
                     // to a handle opened asynchronously.
                     if (errorCode == Interop.Errors.ERROR_INVALID_PARAMETER)
                         throw new IOException(SR.IO_FileTooLongOrHandleNotSync);
-                    throw Win32Marshal.GetExceptionForWin32Error(errorCode, _path);
+                    throw Win32Marshal.GetExceptionForWin32Error(errorCode, _fileHandle.Path);
                 }
             }
             Debug.Assert(r >= 0, "FileStream's WriteCore is likely broken.");
@@ -776,7 +776,7 @@ private unsafe Task<int> ReadNativeAsync(Memory<byte> destination, int numBuffer
                     }
                     else
                     {
-                        throw Win32Marshal.GetExceptionForWin32Error(errorCode, _path);
+                        throw Win32Marshal.GetExceptionForWin32Error(errorCode, _fileHandle.Path);
                     }
                 }
                 else if (cancellationToken.CanBeCanceled) // ERROR_IO_PENDING
@@ -978,7 +978,7 @@ private unsafe Task WriteAsyncInternalCore(ReadOnlyMemory<byte> source, Cancella
                     }
                     else
                     {
-                        throw Win32Marshal.GetExceptionForWin32Error(errorCode, _path);
+                        throw Win32Marshal.GetExceptionForWin32Error(errorCode, _fileHandle.Path);
                     }
                 }
                 else if (cancellationToken.CanBeCanceled) // ERROR_IO_PENDING

src/libraries/System.Private.CoreLib/src/System/IO/Strategies/Net5CompatFileStreamStrategy.cs

@@ -19,9 +19,6 @@ internal sealed partial class Net5CompatFileStreamStrategy : FileStreamStrategy
         /// <summary>Whether the file is opened for reading, writing, or both.</summary>
         private readonly FileAccess _access;
 
-        /// <summary>The path to the opened file.</summary>
-        private readonly string? _path;
-
         /// <summary>The next available byte to be read from the _buffer.</summary>
         private int _readPos;
 
@@ -82,7 +79,6 @@ internal Net5CompatFileStreamStrategy(string path, FileMode mode, FileAccess acc
         {
             string fullPath = Path.GetFullPath(path);
 
-            _path = fullPath;
             _access = access;
             _bufferLength = bufferSize;
 
@@ -293,7 +289,7 @@ internal override SafeFileHandle SafeFileHandle
             }
         }
 
-        internal override string Name => _path ?? SR.IO_UnknownFileName;
+        internal override string Name => _fileHandle.Path ?? SR.IO_UnknownFileName;
 
         internal override bool IsAsync => _useAsyncIO;