Originally raised by nickgeorge at https://chat.fhir.org/#narrow/stream/179175-argonaut/topic/Conditions.20warning.20constraint.20bug

Currently, the us-core-1 constraint on Condition is like this:

where(category.memberOf('http://hl7.org/fhir/us/core/ValueSet/us-core-condition-category')).exists()

But category is a repeating field and memberOf isn't well-defined for input collections with multiple items.

It would be better written as this:

category.where(memberOf('http://hl7.org/fhir/us/core/ValueSet/us-core-condition-category')).exists()

See FHIR-36334 for a related issue where I seek clarification on the memberOf() behavior for input collections with more than a single item.