Validation: conformsTo does not show the error when failing

[oliveregger]

Background when validating with ch-elm, https://fhir.ch/ig/ch-elm/StructureDefinition-PublishDocumentReference.html:

If we test the ConceptMap CH ELM Expecting Specimen Specification To Results Completion Vs and intentionally send a specimen code that is not allowed per valueset ("geni_spec"), then the document is correctly rejected, but the error message is misleading ('Must have a resolvable URL conforming to the CH-ELM Bundle.') and says nothing about the actual problem why it is not conform.

[oliveregger]

we will solve it with a more explicit slicing, increasing the error detail in the invariant is problematic, because we don't know exactly if the the conformsTo error would be the cause of failing the invariant