From 795027efceb599dc62a8c7410fa3396d2460bac0 Mon Sep 17 00:00:00 2001
From: Vlad Zarytovskii <vzaritovsky@hotmail.com>
Date: Mon, 15 Aug 2022 12:09:04 +0200
Subject: [PATCH 1/2] Fix: open shadowcopy file stream for RW

---
 src/Compiler/Utilities/FileSystem.fs          |  6 ++---
 .../Program.fs                                |  1 +
 .../Sample_ConsoleApp_net7.fsproj             | 24 +++++++++++++++++++
 3 files changed, 28 insertions(+), 3 deletions(-)
 create mode 100644 tests/projects/Sample_ConsoleApp_FileSystemTests/Program.fs
 create mode 100644 tests/projects/Sample_ConsoleApp_FileSystemTests/Sample_ConsoleApp_net7.fsproj

diff --git a/src/Compiler/Utilities/FileSystem.fs b/src/Compiler/Utilities/FileSystem.fs
index 791e829a36..7a48804d82 100644
--- a/src/Compiler/Utilities/FileSystem.fs
+++ b/src/Compiler/Utilities/FileSystem.fs
@@ -530,7 +530,7 @@ type DefaultFileSystem() as this =
 
         // We want to use mmaped files only when:
         //   -  Opening large binary files (no need to use for source or resource files really)
-        //   -  Running on mono, since its MemoryMappedFile implementation throws when "mapName" is not provided (is null).
+        //   -  Not running on mono, since its MemoryMappedFile implementation throws when "mapName" is not provided (is null).
         //      (See: https://github.com/mono/mono/issues/10245)
 
         if not useMemoryMappedFile then
@@ -542,12 +542,12 @@ type DefaultFileSystem() as this =
                         MemoryMappedFile.CreateNew(
                             null,
                             length,
-                            MemoryMappedFileAccess.Read,
+                            MemoryMappedFileAccess.ReadWrite,
                             MemoryMappedFileOptions.None,
                             HandleInheritability.None
                         )
 
-                    use stream = mmf.CreateViewStream(0L, length, MemoryMappedFileAccess.Read)
+                    use stream = mmf.CreateViewStream(0L, length, MemoryMappedFileAccess.ReadWrite)
                     fileStream.CopyTo(stream)
                     fileStream.Dispose()
                     mmf
diff --git a/tests/projects/Sample_ConsoleApp_FileSystemTests/Program.fs b/tests/projects/Sample_ConsoleApp_FileSystemTests/Program.fs
new file mode 100644
index 0000000000..75e0a053f4
--- /dev/null
+++ b/tests/projects/Sample_ConsoleApp_FileSystemTests/Program.fs
@@ -0,0 +1 @@
+[<EntryPoint>] let main _ = 0
diff --git a/tests/projects/Sample_ConsoleApp_FileSystemTests/Sample_ConsoleApp_net7.fsproj b/tests/projects/Sample_ConsoleApp_FileSystemTests/Sample_ConsoleApp_net7.fsproj
new file mode 100644
index 0000000000..2b06247db9
--- /dev/null
+++ b/tests/projects/Sample_ConsoleApp_FileSystemTests/Sample_ConsoleApp_net7.fsproj
@@ -0,0 +1,24 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <DisableImplicitFSharpCoreReference>true</DisableImplicitFSharpCoreReference>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <DotnetFscCompilerPath>$(MSBuildThisFileDirectory)../../../artifacts/bin/fsc/Debug/net6.0/fsc.dll</DotnetFscCompilerPath>
+    <Fsc_DotNET_DotnetFscCompilerPath>$(MSBuildThisFileDirectory)../../../artifacts/bin/fsc/Debug/net6.0/fsc.dll</Fsc_DotNET_DotnetFscCompilerPath>
+    <FSharpPreferNetFrameworkTools>False</FSharpPreferNetFrameworkTools>
+    <FSharpPrefer64BitTools>True</FSharpPrefer64BitTools>
+  </PropertyGroup>
+
+  <ItemGroup>
+        <PackageReference Include="FSharp.Core" Version="3.0.2" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Compile Include="Program.fs" />
+  </ItemGroup>
+
+</Project>

From 11d9b08ac79767fb9825e0b5a7254bcc8c91b421 Mon Sep 17 00:00:00 2001
From: Vlad Zarytovskii <vzaritovsky@hotmail.com>
Date: Mon, 15 Aug 2022 19:32:43 +0200
Subject: [PATCH 2/2] Update comment

---
 src/Compiler/Utilities/FileSystem.fs | 2 --
 1 file changed, 2 deletions(-)

diff --git a/src/Compiler/Utilities/FileSystem.fs b/src/Compiler/Utilities/FileSystem.fs
index 7a48804d82..722978e851 100644
--- a/src/Compiler/Utilities/FileSystem.fs
+++ b/src/Compiler/Utilities/FileSystem.fs
@@ -530,8 +530,6 @@ type DefaultFileSystem() as this =
 
         // We want to use mmaped files only when:
         //   -  Opening large binary files (no need to use for source or resource files really)
-        //   -  Not running on mono, since its MemoryMappedFile implementation throws when "mapName" is not provided (is null).
-        //      (See: https://github.com/mono/mono/issues/10245)
 
         if not useMemoryMappedFile then
             fileStream :> Stream