fix: Consistent null handling in BanImplicitDateTimeToDateTimeOffsetConversion

[Copilot]

AnalyzeObjectCreation threw InvalidOperationException when GetTypeByMetadataName returned null, while AnalyzeInvocation handled the same case gracefully via SymbolEqualityComparer.Default.Equals.

Changes

• BanImplicitDateTimeToDateTimeOffsetConversion.cs: Changed AnalyzeObjectCreation to declare nullable INamedTypeSymbol? and return early on null, matching the graceful degradation pattern used throughout the codebase

// Before
INamedTypeSymbol dateTimeOffsetType = context.Compilation.GetTypeByMetadataName("System.DateTimeOffset")
    ?? throw new InvalidOperationException("Unable to find DateTimeOffset type");

// After
INamedTypeSymbol? dateTimeOffsetType = context.Compilation.GetTypeByMetadataName("System.DateTimeOffset");
INamedTypeSymbol? dateTimeType = context.Compilation.GetTypeByMetadataName("System.DateTime");
if (dateTimeOffsetType is null || dateTimeType is null)
{
    return;
}

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[Copilot]

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• pe3vsblobprodcus354.vsblob.vsassets.io
  • Triggering command: /usr/share/dotnet/dotnet dotnet restore --no-dependencies /home/REDACTED/work/CodingGuidelines/CodingGuidelines/Tools/XMLtoMD/GuidelineXmlToMD.sln --packages /tmp/codeql-scratch-ec4d69bafe4e84e6/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/tmp/codeql-scratch-ec4d69bafe4e84e6/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/tmp/codeql-scratch-ec4d69bafe4e84e6/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true (dns block)
  • Triggering command: /usr/share/dotnet/dotnet dotnet restore --no-dependencies /home/REDACTED/work/CodingGuidelines/CodingGuidelines/Tools/XMLtoMD/GuidelineXmlToMD/GuidelineXmlToMD.csproj --packages /tmp/codeql-scratch-ec4d69bafe4e84e6/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/tmp/codeql-scratch-ec4d69bafe4e84e6/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/tmp/codeql-scratch-ec4d69bafe4e84e6/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true (dns block)
  • Triggering command: /usr/share/dotnet/dotnet dotnet restore --no-dependencies /home/REDACTED/work/CodingGuidelines/CodingGuidelines/Tools/XMLtoMD/GuidelineXmlToMD.Test/GuidelineXmlToMD.Test.csproj --packages /tmp/codeql-scratch-ec4d69bafe4e84e6/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/tmp/codeql-scratch-ec4d69bafe4e84e6/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/tmp/codeql-scratch-ec4d69bafe4e84e6/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true (dns block)
• s8mvsblobprodcus38.vsblob.vsassets.io
  • Triggering command: /usr/share/dotnet/dotnet dotnet restore --no-dependencies /tmp/codeql-scratch-ec4d69bafe4e84e6/dbs/csharp/working/152969D1C94CACFB2DD8DDFC3D3B91A8/missingpackages_workingdir --packages /tmp/codeql-scratch-ec4d69bafe4e84e6/dbs/csharp/working/missingpackages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal --configfile /tmp/codeql-scratch-ec4d69bafe4e84e6/dbs/csharp/working/nugetconfig/nuget.config --force (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)