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/10.0.300.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)