C# collection expression support for F# lists & sets

[brianrourkeboll]

Description

• Add support for creating F# lists & sets in C# using C# 12 collection expressions.
  • Language suggestion: Support for C# collection expressions in F# lists and sets fsharp/fslang-suggestions#1355
  • RFC: [RFC FS-1145] C# collection expression support for lists & sets fsharp/fslang-design#776
  • RFC discussion: [RFC FS-1145] C# collection expression support for lists & sets fsharp/fslang-design#777

Examples

FSharpSet<int> xs = [1, 2, 3];

FSharpList<int> ys = [1, 2, 3];

Checklist

• Test cases added.
• Release notes entry updated.

[github-actions]

❗ Release notes required

---

✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
src/FSharp.Core	docs/release-notes/.FSharp.Core/9.0.100.md

[KevinRansom]

This is nice, thanks for this. It's nice to be able to improve C# F# interop.

[brianrourkeboll]

Does anyone know what needs to be done with the new C# test project I added to make the CI happy? Something about the test results needing to be in a certain place, and/or packaging/PDBs?

• https://github.com/dotnet/fsharp/pull/17359/checks?check_run_id=26811754428
• https://dev.azure.com/dnceng-public/public/_build/results?buildId=724144&view=results

*Edit*: Maybe I can figure it out

[brianrourkeboll]

Forgive me if I'm being obtuse, but I don't think I understand the cause of this error in the CI:

PDB0021: Document name doesn't match any pattern in Source Link: '/_1/microsoft.net.test.sdk/17.4.0/build/netcoreapp3.1/Microsoft.NET.Test.Sdk.Program.cs'

The only results on Google are dotnet/runtime#62892 and dotnet/machinelearning#4400, which don't help me much, since I don't understand the underlying problem.

I can see that it comes from here, but... I do not understand why this PR is triggering that.

Is there something obvious I'm missing?

[github-actions]

Failed to run : https://github.com/dotnet/fsharp/actions/runs/9718927879

[brianrourkeboll]

@/vzarytovskii

Do they need to be part of new project? We successfully test interop in component tests.

If we want to put these tests in FSharp.Compiler.ComponentTests/Interop (or, perhaps better, FSharp.Core.UnitTests/Interop), we need to update $(RoslynVersion) to a version that includes C# 12 support:

fsharp/eng/Versions.props

Line 92 in 5c6d8e7

<RoslynVersion>4.6.0-3.23329.3</RoslynVersion>

The version in main (4.6.0-3.23329.3) is a year old. What are the other implications of updating it?

Separately, while it would be nicer from the test writer's perspective to test the consumption of FSharp.Core constructs in C# in an actual C# project, I guess it would have the downside of making it harder to run specific tests against specific versions of C#.

The Roslyn deps were updated in #17144, merged to main today in #17380. I'll try to get these tests to work now.

[github-actions]

Caution

Repository is on lockdown for maintenance, all merges are on hold.

[edgarfgp]

Thanks Brian

[vzarytovskii]

This looks good to me. I'm happy to merge it.

[psfinaki]

Great work, as usual. Thanks!