final protected void verifySummaryFields(String searchName, Map<String, DataType> seenFields) {
        for (DocumentSummary summary : schema.getSummaries().values()) {
            for (SummaryField field : summary.getSummaryFields().values()) {
                if (!field.hasUnresolvedType()) {
                    checkFieldType(searchName, "summary field", field.getName(), field.getDataType(), seenFields);
                }
            }
        }
    }
This Processor makes sure all fields with the same name have the same {@link DataType}. This check
explicitly disregards whether a field is an index field, an attribute or a summary field. This is a requirement if we
hope to move to a model where index fields, attributes and summary fields share a common field class.

@author Simon Thoresen Hult
config-model/src/main/java/com/yahoo/schema/processing/ValidateFieldTypes.java