Follow the instructions below to build and develop the F# Compiler, Core Library and tools on Windows, macOS and Linux.

*[Developing the F# Compiler (Windows)](#developing-the-f-compiler-windows)

*[Developing the F# Compiler (Linux)](#developing-the-f-compiler-linux)

*[Developing the F# Compiler (macOS)](#developing-the-f-compiler-macos)

*[Developing the Visual F# IDE Tools (Windows Only)](#developing-the-visual-f-ide-tools-windows-only)

*[Notes and Resources](#notes)

-[Developing the F# Compiler (Windows)](#developing-the-f-compiler-windows)

-[Developing the F# Compiler (Linux)](#developing-the-f-compiler-linux)

-[Developing the F# Compiler (macOS)](#developing-the-f-compiler-macos)

-[Developing the Visual F# IDE Tools (Windows Only)](#developing-the-visual-f-ide-tools-windows-only)

-[Notes and Resources](#notes)

Install

-[.NET 4.6](https://www.microsoft.com/en-gb/download/details.aspx?id=48130)

**NOTE on Windows:**

1. It is recommended to run the build.cmd and the qualifiers below on a command prompt with path set to have the location of MSBuild. If you have Visual Studio, we can also run using`Developer Command Prompt for Visual Studio 20xx` (depends on Visual Studio version). This developer command prompt is easier to use than normal command prompt, because it already has the correct path of Visual Studio and .NET's tooling set for us to use (including MSBuild).

2. The running command prompt must be run under Administrator right (`Run as Administrator`).

1. It is recommended to run`build.cmd` in a command prompt with path set to have the location of MSBuild. If you have Visual Studio, we can run using`Developer Command Prompt for Visual Studio 20xx` (depends on Visual Studio version). This developer command prompt is easier to use than normal command prompt, because it already has the correct path of Visual Studio and .NET's tooling set for us to use (including MSBuild).

2. The command prompt must have Administrator rights (`Run as Administrator`).

Before running the build scripts, ensure that you have cleaned up the visualfsharp repo by running this git command:

or just build it directly:

If you are just developing the core compiler and library then building``FSharp.sln`` will be enough.

For Linux/Mono, follow[these instructions](http://www.mono-project.com/docs/getting-started/install/linux/). Also you may need:

Then:

Then to replace your machine-wide installation:

Full testing is not yet enabled on Linux.

Install XCode command line tools (or homebrew equivalents) and Mono or Visual Studio for Mac.

Install[the latest .NET SDK](https://www.microsoft.com/net/download/). Then use

Outputs are placed in

Outputs are placed in

This uses an installed .NET SDK 2.0 to build the various duplicated project

Testing the .NET Core version of the F# compiler on macOS and Linux is TBD.

This uses an installed .NET SDK 2.0 to build the various duplicated project

Testing the .NET Core version of the F# compiler on macOS and Linux is TBD.

To build and test Visual F# IDE Tools, install these requirements:

-[Visual Studio 2017](https://www.visualstudio.com/downloads/)

- Under the "Windows" workloads, select ".NET desktop development"

- Select "F# desktop language support" under the optional components

Use``VisualFSharp.sln`` if you're building the Visual F# IDE Tools.

Note on Debug vs Release:``Release`` Configuration has a degraded debugging experience, so if you want to test a change locally, it is recommended to do it in the``Debug`` configuration. For more information seehttps://github.com/Microsoft/visualfsharp/issues/2771 andhttps://github.com/Microsoft/visualfsharp/pull/2773.

Note on Debug vs Release:``Release`` Configuration has a degraded debugging experience, so if you want to test a change locally, it is recommended to do it in the``Debug`` configuration. For more information seeissues[#2771](https://github.com/Microsoft/visualfsharp/issues/2771) and[#2773](https://github.com/Microsoft/visualfsharp/pull/2773).

Note: if you face this error[#2351](https://github.com/Microsoft/visualfsharp/issues/2351):

Note ([#2351](https://github.com/Microsoft/visualfsharp/issues/2351)): if you face this error:

Or hard crash on launch ("Unknown Error"), delete these folders:

For**Debug**, uninstall then reinstall:

For**Release**, uninstall then reinstall:

Restart Visual Studio, it should now be running your freshly-built Visual F# IDE Tools with updated F# Interactive.

To test your changes locally_without_ overwriting your default installed Visual F# tools, set the`VisualFSharp\Vsix\VisualFSharpOpenSource`

To test your changes locally_without_ overwriting your default installed Visual F# tools, set the`VisualFSharp\Vsix\VisualFSharpFull`

project as the startup project. When you hit F5 a new instance of Visual Studio will be started in the`RoslynDev` hive with your

changes, but the root (default) hive will remain untouched. You can also start this hive automatically using

- We use the proto compiler to compile the source for`FSharp.Core.dll` in this distribution.

- We use the proto compiler to compile the source for`FSharp.Compiler.dll`,`fsc.exe`,`fsi.exe`, and other binaries found in this distribution.

If you change error messages you may need to update FSComp.fs in`src\buildfromsource\FSharp.Compiler.Private`.

To do this, build the non-buildfromsource version of FSharp.Compiler.Private (src\fsharp\FSharp.Compiler.Private) then check its obj\ directory for`FSComp.fs` and manually copy that into the buildfromsource directory.

If you are behind a proxy server, NuGet client tool must be configured to use it:

Where you should set proper proxy address, user name and password.

If your changes involve modifying the list of language keywords in any way, (e.g. when implementing a new keyword), the XLF localization files need to be synced with the corresponding resx files. This can be done automatically by running`msbuild FSharp.Compiler.Private.fsproj /t:UpdateXlf` (located in[src\fsharp\FSharp.Compiler.Private](https://github.com/Microsoft/visualfsharp/tree/master/src/fsharp/FSharp.Compiler.Private)). This only works on Windows/.NETStandard framework, so changing this from any other platform requires editing and syncing all of the XLF files manually.

After this, you must copy any differing`resx` files from the output directory into the corresponding subdirectory in[src\buildfromsource](https://github.com/Microsoft/visualfsharp/tree/master/src/fsharp/FSharp.Compiler.Private). This step will soon be eliminated (see issue[#3905](https://github.com/Microsoft/visualfsharp/issues/3905)).

The primary technical guide to the core compiler code is[The F# Compiler Technical Guide](http://fsharp.github.io/2015/09/29/fsharp-compiler-guide.html). Please read and contribute to that guide.

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