Nullability removed when creating anonymous type

[rolfbjarne]

Version Used:

$ dotnet --version
10.0.201

Steps to Reproduce:

Repro: https://lab.razor.fyi/#fY9BSwMxEIXp3jI3exLxMOSk0IZkoQVZREQvCop4FcEY0yWyJiXJbpUlf8R_4L-UDdUtHrwMj_e9x8zAVwFw513t5RtTYfpZgGpkCLj1oAdExBBlNAo7Z17wRhp7dJztHggJ0Rtb48PjGdq2ac69lx94mnX1B7vb3YDe4C_EHumlfm5rOkN6rxstg6aYKgBCOulx7d2rVvHKrlzYdocSEEIGnQW5cHZl6tbLaJzNsZ91s4GnPP-Lj_eNhVTlTxMkmO4t2JLxecnKpVicMCHKg33BGWd8vva6M3ozEnooBONM8B020utChafJ--Qb

Sample code:

string []? nullArray = null;
string []? noNullArray = new string [] { "Debug", "Release" };

var projectInfos = new [] {
	new {
		Configurations = nullArray,
	},
	new {
		Configurations = noNullArray,
	},
};

Expected Behavior:

No warning

Actual Behavior:

warning CS8619: Nullability of reference types in value of type '<anonymous type: string[] Configurations>' doesn't match target type '<anonymous type: string[]? Configurations>'.

It seems the nullable noNullArray ends up being a non-nullable type at some point, causing a type mismatch in the anonymous type.

[MihuBot]

I'm a bot. Here is a possible related and/or duplicate issue (I may be wrong):

• CS8619 is reported on anonymous types #62500

[jjonescz]

Note: this doesn't need arrays, it reproes with just string?, too.

The nullability analysis can see that noNullArray is not null and uses that info for your advantage (e.g., if you call noNullArray.ToString();, you get no warning). However, perhaps it shouldn't use this knowledge to infer the type of an anonymous object in case the source nullability annotation is explicitly given. @RikkiGibson?