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The F# compiler, F# core library, F# language service, and F# tooling integration for Visual Studio

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I have found that Set.intersect have greatly different performance depending on the order of the arguments passed. Here is a reproduction sample ```fsharp type SetIntersectBenchmark() = let longSet = [...

Area-Library
Feature Improvement
Theme-Performance
help wanted

This pull request updates the following dependencies [marker]: (Begin:6bb87d4b-eabe-4492-81b1-19411828fd05) ## From https://github.com/dotnet/roslyn - **Subscription**: [6bb87d4b-eabe-4492-81b1-19411828fd05](https://maestro.dot.net/subscriptions?search=6bb87d4b-eabe-4492-81b1-19411828fd05) - **Build**: [20251210.4](https://dev.azure.com/dnceng/internal/_build/results?buildId=2858332) ([294199](https://maestro.dot.net/channel/7987/github:dotnet:roslyn/build/294199)) - **Date Produced**: December 10, 2025 7:56:58 PM UTC - **Commit**:...

This pull request updates the following dependencies [marker]: (Begin:42c03fd1-399e-4024-0bc2-08db78895535) ## From https://github.com/dotnet/arcade - **Subscription**: [42c03fd1-399e-4024-0bc2-08db78895535](https://maestro.dot.net/subscriptions?search=42c03fd1-399e-4024-0bc2-08db78895535) - **Build**: [20251210.3](https://dev.azure.com/dnceng/internal/_build/results?buildId=2858395) ([294201](https://maestro.dot.net/channel/2/github:dotnet:arcade/build/294201)) - **Date Produced**: December 10, 2025 8:06:59 PM UTC - **Commit**:...

## Description Adds a new compiler warning (FS3879) that detects when triple-slash XML documentation comments (`///`) are not positioned as the first non-whitespace text on a line. This helps developers...

This pull request updates the following dependencies [marker]: (Begin:8fe45351-4600-41f4-ab39-b495b1ed040b) ## From https://github.com/dotnet/arcade - **Subscription**: [8fe45351-4600-41f4-ab39-b495b1ed040b](https://maestro.dot.net/subscriptions?search=8fe45351-4600-41f4-ab39-b495b1ed040b) - **Build**: [20251209.2](https://dev.azure.com/dnceng/internal/_build/results?buildId=2857310) ([293988](https://maestro.dot.net/channel/8394/github:dotnet:arcade/build/293988)) - **Date Produced**: December 9, 2025 4:15:09 PM UTC - **Commit**:...

[View Complete Diff of Changes](https://github.com/dotnet/fsharp/compare/4396154347e812cffb31b5b5b95fdc2028bb4c8c...61c1a22068d208a88f757bd48d5c899db5568837?w=1) - [Centralize Visual Studio installation discovery and assembly resolution in test infrastructure](https://github.com/dotnet/fsharp/pull/19085) - [Fix IL2091 trimming warning in FSharp.Core LazyExtensions.Create](https://github.com/dotnet/fsharp/pull/19114) - [Auto-set FSharpCompilerPath when debugging...

Needs-Triage
vs-insertion

![image](https://user-images.githubusercontent.com/19760720/143722392-2a9aa97e-87d7-4975-9bf1-fcd7236f772c.png) `0]` is strangely colored - a bug. ![image](https://user-images.githubusercontent.com/19760720/143722460-f1231cf3-6aca-4d71-aee6-ed8c65218796.png) `B` is given similarly colored - not sure if this is intended but it seems strange and none of the selectable...

Bug
Impact-Medium
Area-LangService-Colorization

I've created a very simple F# project with 10'000 modules: https://github.com/ners/fsharp-10k Running `dotnet build` in this project appears to never complete; I killed the process after 10 minutes after it...

Bug
Theme-Performance

This PR adds regression tests documenting two consumer-side failures reported in [FSharpPlus issue #613](https://github.com/fsprojects/FSharpPlus/issues/613) that occur with F# 9. ## Overview The tests reproduce real-world FSharpPlus patterns that currently fail...

Currently just replaces cancellable. Features: cold start, multi-start, cancellable, trampolined binds for safe non-tail recursion, fast tail-recursion with `ReturnFromFinal`, exceptions cached in ExceptionDispatchInfo for fast recovery from deep call stacks....