VSSDK006 fires when validation is in another method

[sherryyshi]

I would like to report telemetry when a service is null, so I'm validating my services with another method rather than calling Assumes.Present, or duplicating bunch of if-null blocks. However, VSSDK006 doesn't detect that.

FXCop's CA1602 addresses this by looking at the [ValidatedNotnull] attribute on the validation method (see dotnet/roslyn-analyzers#2863 (comment)). Any chance something similar can be done here?

[AArnott]

Another instance of this occurs here, where is not null is used to test a nullable-annotated field where GetService's result is stored.