foo1.cs

        var pattern = Pattern;

        var constantPattern = pattern as IConstantPattern;
        if (constantPattern != null)
        {
          return IsTypeFromConstantPattern(constantPattern);
        }

        var declarationPattern = pattern as IDeclarationPattern;
        if (declarationPattern != null)
        {
          var typeUsage = declarationPattern.TypeUsage;
          if (typeUsage != null)
          {
            return CSharpTypeFactory.CreateType(typeUsage);
          }
        }

        return TypeFactory.CreateUnknownType(this);

foo2.cs

        switch (Pattern)
        {
          case IConstantPattern constantPattern:
            return IsTypeFromConstantPattern(constantPattern);
          case IDeclarationPattern declarationPattern when declarationPattern.TypeUsage is ITypeUsage typeUsage:
            return CSharpTypeFactory.CreateType(typeUsage);
          default:
            return TypeFactory.CreateUnknownType(this);
        }