From 25e86dbfc6b82ecfc3bbc701a1907bf51e192252 Mon Sep 17 00:00:00 2001
From: Huo Yaoyuan <huoyaoyuan@hotmail.com>
Date: Thu, 28 Jan 2021 23:10:31 +0800
Subject: [PATCH 1/2] Add NotNullWhen(true) on Directory/File.Exists.

---
 src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.cs | 2 +-
 src/libraries/System.IO.FileSystem/src/System/IO/Directory.cs  | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.cs b/src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.cs
index c1790b0658ce64..bf4c13356c1b2c 100644
--- a/src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.cs
+++ b/src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.cs
@@ -126,7 +126,7 @@ public static void Decrypt(string path) { }
         public static void Delete(string path) { }
         [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")]
         public static void Encrypt(string path) { }
-        public static bool Exists(string? path) { throw null; }
+        public static bool Exists([System.Diagnostics.CodeAnalysis.NotNullWhen(true)] string? path) { throw null; }
         public static System.IO.FileAttributes GetAttributes(string path) { throw null; }
         public static System.DateTime GetCreationTime(string path) { throw null; }
         public static System.DateTime GetCreationTimeUtc(string path) { throw null; }
diff --git a/src/libraries/System.IO.FileSystem/src/System/IO/Directory.cs b/src/libraries/System.IO.FileSystem/src/System/IO/Directory.cs
index 4139de67fb83b9..4ffc302bcd70d5 100644
--- a/src/libraries/System.IO.FileSystem/src/System/IO/Directory.cs
+++ b/src/libraries/System.IO.FileSystem/src/System/IO/Directory.cs
@@ -5,6 +5,7 @@
 using System.IO;
 using System.Collections.Generic;
 using System.Linq;
+using System.Diagnostics.CodeAnalysis;
 
 #if MS_IO_REDIST
 using Microsoft.IO.Enumeration;
@@ -49,7 +50,7 @@ public static DirectoryInfo CreateDirectory(string path)
         }
 
         // Tests if the given path refers to an existing DirectoryInfo on disk.
-        public static bool Exists(string? path)
+        public static bool Exists([NotNullWhen(true)] string? path)
         {
             try
             {

From aef304125da9b093032d1c1a6424333669ec872d Mon Sep 17 00:00:00 2001
From: Huo Yaoyuan <huoyaoyuan@hotmail.com>
Date: Fri, 29 Jan 2021 00:24:48 +0800
Subject: [PATCH 2/2] Apply suggestions.

---
 .../System.IO.FileSystem/ref/System.IO.FileSystem.cs          | 4 ++--
 src/libraries/System.IO.FileSystem/src/System/IO/Directory.cs | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.cs b/src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.cs
index bf4c13356c1b2c..64c2bbc309368e 100644
--- a/src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.cs
+++ b/src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.cs
@@ -23,7 +23,7 @@ public static void Delete(string path, bool recursive) { }
         public static System.Collections.Generic.IEnumerable<string> EnumerateFileSystemEntries(string path, string searchPattern) { throw null; }
         public static System.Collections.Generic.IEnumerable<string> EnumerateFileSystemEntries(string path, string searchPattern, System.IO.EnumerationOptions enumerationOptions) { throw null; }
         public static System.Collections.Generic.IEnumerable<string> EnumerateFileSystemEntries(string path, string searchPattern, System.IO.SearchOption searchOption) { throw null; }
-        public static bool Exists([System.Diagnostics.CodeAnalysis.NotNullWhen(true)] string? path) { throw null; }
+        public static bool Exists([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] string? path) { throw null; }
         public static System.DateTime GetCreationTime(string path) { throw null; }
         public static System.DateTime GetCreationTimeUtc(string path) { throw null; }
         public static string GetCurrentDirectory() { throw null; }
@@ -126,7 +126,7 @@ public static void Decrypt(string path) { }
         public static void Delete(string path) { }
         [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")]
         public static void Encrypt(string path) { }
-        public static bool Exists([System.Diagnostics.CodeAnalysis.NotNullWhen(true)] string? path) { throw null; }
+        public static bool Exists([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] string? path) { throw null; }
         public static System.IO.FileAttributes GetAttributes(string path) { throw null; }
         public static System.DateTime GetCreationTime(string path) { throw null; }
         public static System.DateTime GetCreationTimeUtc(string path) { throw null; }
diff --git a/src/libraries/System.IO.FileSystem/src/System/IO/Directory.cs b/src/libraries/System.IO.FileSystem/src/System/IO/Directory.cs
index 4ffc302bcd70d5..3d02ebd98a6beb 100644
--- a/src/libraries/System.IO.FileSystem/src/System/IO/Directory.cs
+++ b/src/libraries/System.IO.FileSystem/src/System/IO/Directory.cs
@@ -2,10 +2,10 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
-using System.IO;
 using System.Collections.Generic;
-using System.Linq;
 using System.Diagnostics.CodeAnalysis;
+using System.IO;
+using System.Linq;
 
 #if MS_IO_REDIST
 using Microsoft.IO.Enumeration;