Support for init-only setter for CA2227: Collection properties should be read only

[madewithsmiles]

Hi, there is no mention about the new init-only (init;) setter feature of C# 9 - https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/proposals/csharp-9.0/init.

From my understanding of this rule, there should not be a violation for properties with init-only setters. If that's the case, how to update this doc and the potential (Roslyn?) analyzer? Thank you :)

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Document Details

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• ID: 019358db-ee31-4b85-6592-f64f54650eac
• Version Independent ID: e177c090-6e1a-5e61-a130-4432f335e8a5
• Content: CA2227: Collection properties should be read only (code analysis) - .NET
• Content Source: docs/fundamentals/code-analysis/quality-rules/ca2227.md
• Product: dotnet-fundamentals
• GitHub Login: @gewarren
• Microsoft Alias: gewarren

[madewithsmiles]

I see this PR in the analyzers repo: dotnet/roslyn-analyzers#4463

So, it's supported. We should add a mention on that in this doc.
I can also validate that "init" is not marked as a violation with Microsoft.CodeAnalysis.NetAnalyzers (Version="5.0.3").