public void handleScalar(ExpressionNode node) {
        if (labels.size() < meta.mappedDims().size()) {
            throw new IllegalArgumentException("At " + address() + ": Missing label for dimension '" +
                                               meta.mappedDims().get(labels.size()) + "'");
        }
        if (meta.type().hasIndexedDimensions()) {
            throw new IllegalArgumentException("At " + address() + ": Need an array of values");
        }
        var addr = new TensorAddress.Builder(meta.type());
        for (int idx = 0; idx < labels.size(); idx++) {
            addr.add(meta.mappedDims().get(idx), labels.get(idx));
        }
        meta.receivingMap().put(addr.build(), TensorFunctionNode.wrapScalar(node));
    }
Helper to incrementally build addresses and insert values (expression nodes) into a map.
Only used as an internal component of the RankingExpression parser.
@author arnej
searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/parser/CellMapHelper.java