docs: private void validateNoAggs(AggFinder aggFinder, SqlNode node,
  		String clause) {
  		final SqlCall agg = aggFinder.findAgg(node);
  		if (agg == null) {
  			return;
  		}
  		final SqlOperator op = agg.getOperator();
  		if (op == SqlStdOperatorTable.OVER) {
  			throw newValidationError(agg,
  				RESOURCE.windowedAggregateIllegalInClause(clause));
  		} else if (op.isGroup() || op.isGroupAuxiliary()) {
  			throw newValidationError(agg,
  				RESOURCE.groupFunctionMustAppearInGroupByClause(op.getName()));
  		} else {
  			throw newValidationError(agg,
  				RESOURCE.aggregateIllegalInClause(clause));
  		}
  	}