private void fail(DocumentSummary summary, SummaryField field, String msg) {
        throw new IllegalArgumentException(formatError(schema, summary, field, msg));
    }
Iterates all summary fields with 'matched-elements-only' or 'select-elements-by' and validates that the field type is supported.

@author geirst
config-model/src/main/java/com/yahoo/schema/processing/SummaryElementsSelectorValidator.java