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Add polyfills for C# 15 union types (UnionAttribute and IUnion) - #140
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Sergio0694 merged 5 commits intoOct 26, 2026
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AndiJingzhiTse
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.NET 11 RC is out and it already has |
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@Sergio0694 mind kicking off the workflow? Assuming it drops an accessible artifact, I can try the private build in my project for final testing. |
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Approved! I'll try to get to this PR later this week 🙂 |
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I pulled the NuGet package from the pipeline to test locally in my .NET 8 Godot project swapping out my manual proxies. I see the generator adding them in and it works like a charm! 🚀
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Any update on this? |
Adds source-only polyfills for the UnionAttribute and IUnion interface from System.Runtime.CompilerServices, enabling C# 15 union type features on downlevel targets before .NET 11 ships these types in the BCL. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
…e.CompilerServices.UnionAttribute.cs Co-authored-by: Theodore Tsirpanis <teo@tsirpanis.gr>
Co-authored-by: Theodore Tsirpanis <teo@tsirpanis.gr>
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Synchronize README entries, align API documentation, and cover generated and manual unions with non-boxing accessors. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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Summary
Closes #139
This PR adds source-only polyfills for the two types required by the C# 15 union types feature, enabling their use on downlevel targets before .NET 11 ships these types in the BCL:
[Union](System.Runtime.CompilerServices.UnionAttribute) — attribute recognized by the C# 15 compiler to identify a type as a union typeIUnion(System.Runtime.CompilerServices.IUnion) — interface that union types implement, providing access to the underlying value viaobject? Value { get; }Both are placed in the main
EmbeddedResources/folder (language support polyfills, enabled by default) and follow the existing conventions:// <auto-generated/>header,internalaccessibility (switchable topublicviaPolySharpUsePublicAccessibilityForGeneratedTypes), and[ExcludeFromCodeCoverage]on the attribute class.References
Test plan
TestUnionclass intests/PolySharp.Tests/LanguageFeatures.csthat applies[Union]and implementsIUnion, exercising both new polyfillsdotnet build— 0 warnings, 0 errorsnet472,net48,net481,netstandard2.0,netstandard2.1,net8.0,net9.0)🤖 Generated with Claude Code