New Collection expressions initializer allows null for non nullable Collections

[TheCell]

Is this a Visual Studio Problem, C# Problem or is that allowed behaviour?

This Code compiles and runs, resulting in a list with one entry that is null, even though the List accepts only non nullable strings.

string? testString = null;
List<string> testList = [testString];

This code does not compile:

List<string> testList3 = new List<string> { null };
List<string> testList4 = new List<string>();
testList4.Add(null);

We are using the Roslyn analyzer.
Our Solution is using the following:

<Nullable>enable</Nullable>
<WarningsAsErrors>nullable</WarningsAsErrors>
<EnableNETAnalyzers>true</EnableNETAnalyzers>
<AnalysisLevel>latest</AnalysisLevel>

I think that's a bug?

[HaloFour]

Both snippets of code compile successfully. The C# compiler will issue warnings about potential nulls, but it is not a compiler error. Are you using a third-party analyzer in Visual Studio, like R#? That might be giving you the errors on the second code snippet.

[TheCell]

Using the Roslyn analyzer.

Our Solution is using the following:

<Nullable>enable</Nullable>
<WarningsAsErrors>nullable</WarningsAsErrors>
<EnableNETAnalyzers>true</EnableNETAnalyzers>
<AnalysisLevel>latest</AnalysisLevel>

[333fred]

This looks like dotnet/roslyn#71522, @RikkiGibson to confirm.

[dlebansais]

There are about five different ways to insert null values in your program without the compiler or analyzers noticing. I wouldn't call that a bug, but a limitation of what they can do to help you find the error before the code throws an exception at runtime.

[cston]

This is one of the remaining work items in dotnet/roslyn#68786:

• Checking conversion of elements to iteration type for collection initializer types