private void executeStructField(StructuredFieldValue struct, ExecutionContext context) {
        Field field = struct.getField(structFieldName);
        if (field == null)
            throw new IllegalArgumentException("In " + this +": Field '" + structFieldName + "' not found in struct type '" +
                                               struct.getDataType().getName() + "'");
        context.setCurrentValue(struct.getFieldValue(field));
    }
Returns the value of a struct field.

@author Simon Thoresen Hult
indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/GetFieldExpression.java