FCS namespace revamp

[dsyme]

This a revamp of the namespace and naming of FCS following on from a design review with @TIHan @jonsequitur @cartermp @KevinRansom

Namespaces are:

FSharp.Compiler.IO  // FileSystem
FSharp.Compiler.CodeAnalysis // FSharpChecker, FSharpCheckFileResults, FSharpChecProjectResults and friends
FSharp.Compiler.Diagnostics     // FSharpDiagnostic and friends
FSharp.Compiler.EditorServices // Misc functionality for editors, e.g. interface stub generation
FSharp.Compiler.Interactive.Shell // F# Interactive
FSharp.Compiler.Symbols           // FSharpEntity etc
FSharp.Compiler.Syntax           // Types and functionality for syntax tree
FSharp.Compiler.Text           // ISourceFile, Range, TaggedText and other things
FSharp.Compiler.Tokenization      // FSharpLineTokenizer etc.

Changes are documented in release-notes.md

Other internal cleanup changes:

• dead code removed in vsintegration/src/FSharp.LanguageService/ProjectSitesAndFiles.fs

TODO in later PRs:

• Switch to ImmutableArray instead of IList through the Symbols API

• Add an immutable, extensible, binary-compati-maintainable API to give binary-compatible access to the syntax tree

[cartermp]

This is only correct if we plan on getting this in for FCS 39, which to my knowledge isn't the case? At least not that I'm aware of

[dsyme]

I don't mind - just let me know the schedule.

(TBH I'm ok with delaying 39 until this is in, even if it's not 100% complete it's still better to get the foundational renames into the ecosystem. But I don't know if there are people desperate to get 39 or not)

[cartermp]

We need to, at a minimum, release FCS 39 with VS 16.9. VS 16.9 bits are locked down for bug fixes only. So I highly doubt we'd incorporate this right now since it's helpful from a coherency standpoint - until we have a shipping cadence for FCS properly established - to have bits map to one another cleanly.

[cartermp]

FCS 39 would come with a bunch of bug fixes and improvements already, so folks definitely would want it

[baronfel]

Yep, eagerly anticipating a drop of 39 (since the nightlies aren't usable for packaging reasons :) ).

[dsyme]

OK great thank you. So I think that means we can integrate this to master and not into 16.9 release branch? I'll make sure the release notes are separate under 40.0

[dsyme]

Aside: It did occur to me that perhaps the naming should be as follows to match the DLL, though I don't really mind

FSharp.Compiler.Service.IO  // FileSystem
FSharp.Compiler.Service.CodeAnalysis // FSharpChecker, FSharpCheckFileResults, FSharpChecProjectResults and friends
FSharp.Compiler.Service.Diagnostics     // FSharpDiagnostic and friends
FSharp.Compiler.Service.EditorServices // Misc functionality for editors, e.g. interface stub generation
FSharp.Compiler.Service.Syntax           // Types and functionality for syntax tree
FSharp.Compiler.Service.Interactive.Shell // F# Interactive

[NinoFloris]

FSharp.CompilerServices maybe?

[cartermp]

why this change?

[dsyme]

ImmutableArray is not in the default reference set for F# Interactive (i.e. the default reference set for the F# scripting model) and in my testing this is causing problems when using the API (though I could just reference it in my test scripts)

We can still use ImmutableArray but I just wanted to do it all-at-once intentionally (replacing all uses of IList<_> by ImmutableArray<_> for example) and also remembering to fix this problem.

I'll make a note of this at the top of this PR

[dsyme]

FSharp.CompilerServices maybe?

I quite like this name.

FSharp.CompilerServices.IO  // FileSystem
FSharp.CompilerServices.CodeAnalysis // FSharpChecker, FSharpCheckFileResults, FSharpChecProjectResults and friends
FSharp.CompilerServices.Diagnostics     // FSharpDiagnostic and friends
FSharp.CompilerServices.EditorServices // Misc functionality for editors, e.g. interface stub generation
FSharp.CompilerServices.Interactive.Shell // F# Interactive
FSharp.CompilerServices.Symbols           // FSharpEntity etc
FSharp.CompilerServices.Syntax           // Types and functionality for syntax tree
FSharp.CompilerServices.Text           // ISourceFile, Range, TaggedText and other things
FSharp.CompilerServices.Tokenization      // FSharpLineTokenizer etc.

[dsyme]

This PR is ready (once green). It's large but nearly entirely routine.

Would appreciate getting it merged fairly rapidly to minimise maintenance and get it integrated against all other ongoing work.

[dsyme]

Thank you for the quick merge!!!