adding test, conditional check

src/fhirtypes/StructureDefinition.ts

@@ -691,7 +691,18 @@ export class StructureDefinition {
       ) {
         // We throw an error if the currentElement doesn't exist, has been zeroed out,
         // or is being incorrectly accessed as an array
-        throw new CannotResolvePathError(path);
+        if (
+          pathPart.base === 'concept' &&
+          pathPart.brackets[0] === 'undefined' &&
+          pathPart.slices[0] === 'undefined'
+        ) {
+          throw new Error(
+            'This rule is invalid. The rule does not contain a concept array in the compose element with the code system given.'
+          );
+          // TODO: code system --> fisher.tank.docs[0].valueSets[0].value.rules[0].from.system
+        } else {
+          throw new CannotResolvePathError(path);
+        }
       }
 
       // Determine if base and/or current are arrays. Note that this is not perfect (if base or current max is missing),

test/export/ValueSetExporter.test.ts

@@ -723,6 +723,31 @@ describe('ValueSetExporter', () => {
     });
   });
 
+  it('should throw error for caret rule on valueset compose component without any concept', () => {
+    // ValueSet: SomeVS
+    // * include codes from system http://example.org/CS
+    // * http://example.org/CS#"some-code" ^designation.value = "some value"
+
+    const valueSet = new FshValueSet('SomeVS');
+
+    const component = new ValueSetConceptComponentRule(true);
+    component.from.system = 'http://example.org/CS';
+
+    const cvRule = new CaretValueRule('');
+    cvRule.pathArray = ['http://example.org/CS#"some-code"'];
+    cvRule.caretPath = 'designation.value';
+    cvRule.value = 'some value';
+
+    valueSet.rules.push(component, cvRule);
+    doc.valueSets.set(valueSet.name, valueSet);
+    const exported = exporter.export().valueSets;
+    expect(exported.length).toBe(1);
+    expect(loggerSpy.getAllMessages('error')).toHaveLength(1);
+    expect(loggerSpy.getLastMessage('error')).toMatch(
+      /This rule is invalid. The rule does not contain a concept array in the compose element/
+    );
+  });
+
   it('should remove and log error when exporting a value set that includes a component from a self referencing value set', () => {
     const valueSet = new FshValueSet('DinnerVS');
     valueSet.id = 'dinner-vs';