What's new in F# 10

[abonie]

Summary

Article about new changes in F# 10

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Internal previews

📄 File	🔗 Preview link
docs/core/whats-new/dotnet-10/overview.md	What's new in .NET 10
docs/fsharp/language-reference/computation-expressions.md	Computation Expressions
docs/fsharp/language-reference/parameters-and-arguments.md	Parameters and arguments
docs/fsharp/whats-new/fsharp-10.md	docs/fsharp/whats-new/fsharp-10

[Copilot]

Pull Request Overview

This PR adds comprehensive documentation for F# 10 features. The document introduces new language features, library improvements, and tooling enhancements available in F# 10 that ships with .NET 10 and Visual Studio 2022.

Key changes:

• New documentation file covering 11 major F# 10 features including scoped warning suppression, access modifiers on auto properties, ValueOption optional parameters, tail-call support in computation expressions, and parallel compilation.
• Detailed examples with code snippets demonstrating before/after patterns for each feature.
• Breaking changes and compatibility notes are clearly highlighted throughout.

[BillWagner]

Thanks @abonie

This is a great draft. I had a couple comments to consider.

[abonie]

Thanks @abonie

This is a great draft. I had a couple comments to consider.

Thanks for the feedback! I have made some changes based on your comments @BillWagner

[abonie]

@BillWagner @gewarren I have copy-pasted this metadata section from a previous article and I simply guessed that ms.date is preferred publication date, let me know if that's wrong

[T-Gro]

Since this is docs, I feel like this page should also have some info w.r.t to the type cache now part of the compiler.
Not so much hyping it, but rather the ways it can be controlled via switches/env vars so that people have a way to react if they are unhappy with the memory profile or eviction mechanics (after all people might be compiling on machines we did not have a chance to test it on).

@majocha , @abonie -
I imagine the following user guidance:

• To turn it off, fallback to <LangVersion>9<..>
• To turn off eviction via dedicated agents (= increases thread pressure) and replace it with sync eviction use the FSharp_CacheEvictionImmediate=1 env var

[abonie]

Hmm... I decided to omit it from the docs since it is more of an implementation detail, doesn't even have its own dedicated setting(?) and keep it for the blog. But I see your point.

In that case, is there a specific situation/symptom that might point to issues with type cache? So I can say e.g. "If <specific condition> and you see longer compilation times after updating, then consider falling back to F# 9 via LangVersion". Also, if we're expecting that a significant portion of users might want to turn this off, should we have a dedicated setting for the type subsumption cache?

[T-Gro]

I would go with:

• Increased memory footprint
• Increased CPU usage (due to type eviction spinning up additional workers to maintain the cache under churn)