internal GroupKeyAggregateInfo( GroupAggregateKind aggregateKind, ErrorContext errCtx, GroupAggregateInfo containingAggregate, ScopeRegion definingScopeRegion) : base( aggregateKind, null /* there is no AST.GroupAggregateExpression corresponding to the group key */, errCtx, containingAggregate, definingScopeRegion) { }