missing guidance on null guards

[bitbonk]

There has been some discussion and misunderstanding on whether or not application and/or library developers now can remove any null guards (e.g. if(input != null){...}, ArgumentNullException) because of this feature. See for example here and here. The documentation needs clear guidance if or if not (and if so, when) it is now safe to remove null guards.

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Document Details

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• ID: bea1e2ab-5517-b17c-4a65-7c7bae09261a
• Version Independent ID: 2a326631-709b-4461-6c15-a75a5087ef1d
• Content: Nullable reference types in C# - C# 8.0 language proposals
• Content Source: proposals/csharp-8.0/nullable-reference-types.md
• Product: dotnet-csharp
• Technology: csharp-spec
• GitHub Login: @dotnet-bot
• Microsoft Alias: wiwagn

[BillWagner]

Thanks for writing this @bitbonk

The reference guidance for corefx is a good start. However, as we add more annotations to different APIs in corefx, we're continuing to learn the best way forward. We're not comfortable saying "we know the answers" yet.

I've not assigned this a milestone, because we're not confident enough of the current guidance to recommend it universally. However, I've adding a high priority label because we agree it's important.