Repository: dotnet/aspnetcore
File: src/Http/Http.Extensions/gen/Microsoft.AspNetCore.Http.ValidationsGenerator/Parsers/ValidationsGenerator.TypesParser.cs (C#)

Code before:
namespace Microsoft.AspNetCore.Http.ValidationsGenerator;

public sealed partial class ValidationsGenerator : IIncrementalGenerator
{
    private static readonly SymbolDisplayFormat _symbolDisplayFormat = new(
        globalNamespaceStyle: SymbolDisplayGlobalNamespaceStyle.Included,
        typeQualificationStyle: SymbolDisplayTypeQualificationStyle.NameAndContainingTypesAndNamespaces);

    internal ImmutableArray<ValidatableType> ExtractValidatableTypes(IInvocationOperation operation, WellKnownTypes wellKnownTypes)
    {
        AnalyzerDebug.Assert(operation.SemanticModel != null, "SemanticModel should not be null.");
        var parameters = operation.TryGetRouteHandlerMethod(operation.SemanticModel, out var method)
            ? method.Parameters
            : [];

        var fromServiceMetadataSymbol = wellKnownTypes.Get(
            WellKnownTypeData.WellKnownType.Microsoft_AspNetCore_Http_Metadata_IFromServiceMetadata);

        var validatableTypes = new HashSet<ValidatableType>(ValidatableTypeComparer.Instance);
        List<ITypeSymbol> visitedTypes = [];

        foreach (var parameter in parameters)
        {
            // Skip attributes that implement the IFromServiceMetadata interface.
            // These attributes are used for dependency injection (DI) purposes and do not require validation.
            if (parameter.GetAttributes().Any(attr => attr.AttributeClass is not null && attr.AttributeClass.ImplementsInterface(fromServiceMetadataSymbol)))
            {
                continue;
            }

            _ = TryExtractValidatableType(parameter.Type, wellKnownTypes, ref validatableTypes, ref visitedTypes);
        }
        return [.. validatableTypes];
    }

    internal bool TryExtractValidatableType(ITypeSymbol incomingTypeSymbol, WellKnownTypes wellKnownTypes, ref HashSet<ValidatableType> validatableTypes, ref List<ITypeSymbol> visitedTypes)
    {
        var typeSymbol = incomingTypeSymbol.UnwrapType(wellKnownTypes.Get(WellKnownTypeData.WellKnownType.System_Collections_IEnumerable));
        if (typeSymbol.SpecialType != SpecialType.None)
        {
            return false;
        }

        if (visitedTypes.Contains(typeSymbol))
        {
            return true;
        }

        if (typeSymbol.IsExemptType(wellKnownTypes))
        {
            return false;

Review comment (suggestion):
Should also add a check for `[FromKeyedServicesAttribute]` (and test of course)

Code after:
namespace Microsoft.AspNetCore.Http.ValidationsGenerator;

public sealed partial class ValidationsGenerator : IIncrementalGenerator
{
    private static readonly SymbolDisplayFormat _symbolDisplayFormat = new(
        globalNamespaceStyle: SymbolDisplayGlobalNamespaceStyle.Included,
        typeQualificationStyle: SymbolDisplayTypeQualificationStyle.NameAndContainingTypesAndNamespaces);

    internal ImmutableArray<ValidatableType> ExtractValidatableTypes(IInvocationOperation operation, WellKnownTypes wellKnownTypes)
    {
        AnalyzerDebug.Assert(operation.SemanticModel != null, "SemanticModel should not be null.");
        var parameters = operation.TryGetRouteHandlerMethod(operation.SemanticModel, out var method)
            ? method.Parameters
            : [];

        var fromServiceMetadataSymbol = wellKnownTypes.Get(
            WellKnownTypeData.WellKnownType.Microsoft_AspNetCore_Http_Metadata_IFromServiceMetadata);
        var fromKeyedServiceAttributeSymbol = wellKnownTypes.Get(
            WellKnownTypeData.WellKnownType.Microsoft_Extensions_DependencyInjection_FromKeyedServicesAttribute);

        var validatableTypes = new HashSet<ValidatableType>(ValidatableTypeComparer.Instance);
        List<ITypeSymbol> visitedTypes = [];

        foreach (var parameter in parameters)
        {
            // Skip parameters that are injected as services
            if (parameter.IsServiceParameter(fromServiceMetadataSymbol, fromKeyedServiceAttributeSymbol))
            {
                continue;
            }

            _ = TryExtractValidatableType(parameter.Type, wellKnownTypes, ref validatableTypes, ref visitedTypes);
        }
        return [.. validatableTypes];
    }

    internal bool TryExtractValidatableType(ITypeSymbol incomingTypeSymbol, WellKnownTypes wellKnownTypes, ref HashSet<ValidatableType> validatableTypes, ref List<ITypeSymbol> visitedTypes)
    {
        var typeSymbol = incomingTypeSymbol.UnwrapType(wellKnownTypes.Get(WellKnownTypeData.WellKnownType.System_Collections_IEnumerable));
        if (typeSymbol.SpecialType != SpecialType.None)
        {
            return false;
        }

        if (visitedTypes.Contains(typeSymbol))
        {
            return true;
        }

        if (typeSymbol.IsExemptType(wellKnownTypes))
        {