Updating the compiler sources

From time to time we want to update the sources of the F# compiler we use for our own parser (Fantomas.FCS).
Reasons can be bugfixes or new features we want to use. Examples are range fixes or newly added information in the AST we want to make use of.

To do this, first remove the old compiler sources by running:

git clean -xdf

Make sure, that this removes your .deps folder.
Next update the hash of the source version to use. Edit the FCSCommitHash value in the Directory.Build.props file. Run

dotnet fsi .\build.fsx -p Init

to download the new sources into the .deps folder. Make sure there's one directory in .deps named like the configured hash afterwards.

You can now run a build to see if there is any obvious breakage:

dotnet build

If not, you can run the Fantomas.Core tests next

cd ./src/Fantomas.Core.Tests
dotnet test

Even if the tests are all green you should take a look at all the changes made to the SyntaxTree and make sure these changes don't need further adjustments in Fantomas.

Think about tests to catch any regressions caused by the update and it's effects on Fantomas.