/// <inheritdoc cref="GroupingAnalyzer{S,M}.Preconditions"/> public override IEnumerable <Action <StructType> > Preconditions() => new[] { AnalyzersExt.AtLeastOne(Columns) } .Concat(Columns.Select(AnalyzersExt.HasColumn)) .Concat(Columns.Select(AnalyzersExt.IsNotNested)) .Concat(base.Preconditions());