ref declarations and src empty definitions

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

@@ -48,6 +48,17 @@ public static DirectoryInfo CreateDirectory(string path)
             return new DirectoryInfo(path, fullPath, isNormalized: true);
         }
 
+        /// <summary>
+        /// Creates a directory symbolic link identified by <paramref name="path"/> that points to <paramref name="pathToTarget"/>.
+        /// </summary>
+        /// <param name="path">The location of the directory symbolic link.</param>
+        /// <param name="pathToTarget">The target of the directory symbolic link.</param>
+        /// <returns>A <see cref="DirectoryInfo"/> instance that wraps the newly created directory symbolic link.</returns>
+        public static FileSystemInfo CreateSymbolicLink(string path, string pathToTarget)
+        {
+            return new DirectoryInfo("");
+        }
+
         // Tests if the given path refers to an existing DirectoryInfo on disk.
         public static bool Exists([NotNullWhen(true)] string? path)
         {
@@ -315,5 +326,16 @@ public static string[] GetLogicalDrives()
         {
             return FileSystem.GetLogicalDrives();
         }
+
+        /// <summary>
+        /// Gets the target of the specified directory symbolic link.
+        /// </summary>
+        /// <param name="linkPath">The path of the directory symbolic link.</param>
+        /// <param name="returnFinalTarget"><see langword="true"/> to follow links to the final target; <see langword="false"/> to return the immediate next link.</param>
+        /// <returns>A <see cref="DirectoryInfo"/> instance if the symbolic link exists, independently if the target exists or not. <see langword="null"/> if the symbolic link does not exist.</returns>
+        public static System.IO.FileSystemInfo? ResolveLinkTarget(string linkPath, bool returnFinalTarget = false)
+        {
+            return null;
+        }
     }
 }

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

@@ -99,6 +99,17 @@ public static FileStream Create(string path, int bufferSize)
         public static FileStream Create(string path, int bufferSize, FileOptions options)
             => new FileStream(path, FileMode.Create, FileAccess.ReadWrite, FileShare.None, bufferSize, options);
 
+        /// <summary>
+        /// Creates a file symbolic link identified by <paramref name="path"/> that points to <paramref name="pathToTarget"/>.
+        /// </summary>
+        /// <param name="path">The location of the file symbolic link.</param>
+        /// <param name="pathToTarget">The target of the file symbolic link.</param>
+        /// <returns>A <see cref="FileInfo"/> instance that wraps the newly created file symbolic link.</returns>
+        public static FileSystemInfo CreateSymbolicLink(string path, string pathToTarget)
+        {
+            return new FileInfo("");
+        }
+
         // Deletes a file. The file specified by the designated path is deleted.
         // If the file does not exist, Delete succeeds without throwing
         // an exception.
@@ -1007,5 +1018,16 @@ private static async Task InternalWriteAllTextAsync(StreamWriter sw, string cont
                 ? Task.FromCanceled(cancellationToken)
                 : InternalWriteAllLinesAsync(AsyncStreamWriter(path, encoding, append: true), contents, cancellationToken);
         }
+
+        /// <summary>
+        /// Gets the target of the specified file symbolic link.
+        /// </summary>
+        /// <param name="linkPath">The path of the file symbolic link.</param>
+        /// <param name="returnFinalTarget"><see langword="true"/> to follow links to the final target; <see langword="false"/> to return the immediate next link.</param>
+        /// <returns>A <see cref="FileInfo"/> instance if the symbolic link exists, independently if the target exists or not. <see langword="null"/> if the symbolic link does not exist.</returns>
+        public static System.IO.FileSystemInfo? ResolveLinkTarget(string linkPath, bool returnFinalTarget = false)
+        {
+            return null;
+        }
     }
 }

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

@@ -107,6 +107,25 @@ public DateTime LastWriteTimeUtc
             set => LastWriteTimeCore = File.GetUtcDateTimeOffset(value);
         }
 
+        /// <summary>
+        /// If this <see cref="FileSystemInfo"/> instance represents a link, returns the link target's path.
+        /// If the link does not exist, returns <see langword="null"/>.
+        /// </summary>
+        public string? LinkTarget { get { return null; } }
+
+        /// <summary>
+        /// Creates a symbolic link located in <see cref="FullName"/> that points to the specified <paramref name="pathToTarget"/>.
+        /// </summary>
+        /// <param name="pathToTarget">The path of the symbolic link target.</param>
+        public void CreateAsSymbolicLink(string pathToTarget) { }
+
+        /// <summary>
+        /// Gets the target of the specified symbolic link.
+        /// </summary>
+        /// <param name="returnFinalTarget"><see langword="true"/> to follow links to the final target; <see langword="false"/> to return the immediate next link.</param>
+        /// <returns>A <see cref="FileInfo"/> instance if the symbolic link exists, independently if the target exists or not. <see langword="null"/> if the symbolic link does not exist.</returns>
+        public System.IO.FileSystemInfo? ResolveLinkTarget(bool returnFinalTarget = false) { return null; }
+
         /// <summary>
         /// Returns the original path. Use FullName or Name properties for the full path or file/directory name.
         /// </summary>

src/libraries/System.Runtime/ref/System.Runtime.cs

@@ -7412,6 +7412,7 @@ public override void WriteByte(byte value) { }
     public static partial class Directory
     {
         public static System.IO.DirectoryInfo CreateDirectory(string path) { throw null; }
+        public static System.IO.FileSystemInfo CreateSymbolicLink(string path, string pathToTarget) { throw null; }
         public static void Delete(string path) { }
         public static void Delete(string path, bool recursive) { }
         public static System.Collections.Generic.IEnumerable<string> EnumerateDirectories(string path) { throw null; }
@@ -7450,6 +7451,7 @@ public static void Delete(string path, bool recursive) { }
         public static string[] GetLogicalDrives() { throw null; }
         public static System.IO.DirectoryInfo? GetParent(string path) { throw null; }
         public static void Move(string sourceDirName, string destDirName) { }
+        public static System.IO.FileSystemInfo? ResolveLinkTarget(string linkPath, bool returnFinalTarget = false) { throw null; }
         public static void SetCreationTime(string path, System.DateTime creationTime) { }
         public static void SetCreationTimeUtc(string path, System.DateTime creationTimeUtc) { }
         public static void SetCurrentDirectory(string path) { }
@@ -7474,10 +7476,13 @@ protected FileSystemInfo(System.Runtime.Serialization.SerializationInfo info, Sy
         public System.DateTime LastAccessTimeUtc { get { throw null; } set { } }
         public System.DateTime LastWriteTime { get { throw null; } set { } }
         public System.DateTime LastWriteTimeUtc { get { throw null; } set { } }
+        public string? LinkTarget { get { throw null; } }
         public abstract string Name { get; }
+        public void CreateAsSymbolicLink(string pathToTarget) { }
         public abstract void Delete();
         public virtual void GetObjectData(System.Runtime.Serialization.SerializationInfo info, System.Runtime.Serialization.StreamingContext context) { }
         public void Refresh() { }
+        public System.IO.FileSystemInfo? ResolveLinkTarget(bool returnFinalTarget = false) { throw null; }
         public override string ToString() { throw null; }
     }
     public sealed partial class DirectoryInfo : System.IO.FileSystemInfo
@@ -7562,6 +7567,7 @@ public static void Copy(string sourceFileName, string destFileName, bool overwri
         public static System.IO.FileStream Create(string path) { throw null; }
         public static System.IO.FileStream Create(string path, int bufferSize) { throw null; }
         public static System.IO.FileStream Create(string path, int bufferSize, System.IO.FileOptions options) { throw null; }
+        public static System.IO.FileSystemInfo CreateSymbolicLink(string path, string pathToTarget) { throw null; }
         public static System.IO.StreamWriter CreateText(string path) { throw null; }
         [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")]
         public static void Decrypt(string path) { }
@@ -7600,6 +7606,7 @@ public static void Move(string sourceFileName, string destFileName, bool overwri
         public static System.Collections.Generic.IEnumerable<string> ReadLines(string path, System.Text.Encoding encoding) { throw null; }
         public static void Replace(string sourceFileName, string destinationFileName, string? destinationBackupFileName) { }
         public static void Replace(string sourceFileName, string destinationFileName, string? destinationBackupFileName, bool ignoreMetadataErrors) { }
+        public static System.IO.FileSystemInfo? ResolveLinkTarget(string linkPath, bool returnFinalTarget = false) { throw null; }
         public static void SetAttributes(string path, System.IO.FileAttributes fileAttributes) { }
         public static void SetCreationTime(string path, System.DateTime creationTime) { }
         public static void SetCreationTimeUtc(string path, System.DateTime creationTimeUtc) { }