Add #version;; directive to F# Interactive

[bbatsov]

Description

Users with multiple F#/SDK/VS installations often need to identify which FSI they're running. The startup banner shows the version, but it scrolls away quickly. This adds a #version;; directive that prints version and environment info on demand — useful for debugging and bug reporting.

Example output:

Microsoft (R) F# Interactive version 12.9.100.0 for F# 9.0
.NET: .NET 9.0.0
OS: Darwin 24.1.0 (Arm64)

Fixes #13307

Checklist

• Test cases added
• Performance benchmarks added in case of performance changes
• Release notes entry updated

[github-actions]

❗ Release notes required

---

✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/11.0.100.md

[T-Gro]

Thank you 👍 .

Two bonus ideas if doable and if you think they are good additions:

The same F# binary can be configured (VS options, directory.props,..) to serve different F# Language version, maybe show that as well?

The same for FSharp.Core version - often not clear where FSharp.Core comes from (from VS, from SDK, from project,...).

From a perspective of a person who reads bugs reports, all of those make sense 👍 .

[bbatsov]

Done! I've added both the F# language version and FSharp.Core version to the output. #version;; now prints something like:

Microsoft (R) F# Interactive version 12.9.100.0 for F# 9.0
Language Version: 9.0
FSharp.Core: 9.0.0.0
.NET: .NET 9.0.0
OS: Darwin 24.1.0 (Arm64)

[T-Gro]

Thanks for doing the additions, this is nice 👍

[bbatsov]

Moved the release notes entry from 10.0.300.md to 11.0.100.md because the CI check is looking for the latter. Not sure if that's the right file or if the check is misconfigured — happy to move it back if needed.