Program: 112201
Project: 112201
Buggy source:
private void checkReference(Object appContext,List<ValidationMessage> errors,String path,Element element,StructureDefinition profile,ElementDefinition container,String parentType,NodeStack stack) throws FHIRException, IOException {
  Reference reference=readAsReference(element);
  String ref=reference.getReference();
  if (Utilities.noString(ref)) {
    if (Utilities.noString(reference.getIdentifier().getSystem()) && Utilities.noString(reference.getIdentifier().getValue())) {
      warning(errors,IssueType.STRUCTURE,element.line(),element.col(),path,!Utilities.noString(element.getNamedChildValue("String_Node_Str")),"String_Node_Str");
    }
    return;
  }
  Element we=localResolve(ref,stack,errors,path);
  String refType;
  if (ref.startsWith("String_Node_Str")) {
    refType="String_Node_Str";
  }
 else {
    if (we == null) {
      refType="String_Node_Str";
    }
 else {
      refType="String_Node_Str";
    }
  }
  String ft;
  if (we != null)   ft=we.getType();
 else   ft=tryParse(ref);
  ReferenceValidationPolicy pol=refType.equals("String_Node_Str") ? ReferenceValidationPolicy.CHECK_VALID : fetcher == null ? ReferenceValidationPolicy.IGNORE : fetcher.validationPolicy(appContext,path,ref);
  if (pol.checkExists()) {
    if (we == null) {
      if (fetcher == null)       throw new FHIRException("String_Node_Str");
      we=fetcher.fetch(appContext,ref);
    }
    rule(errors,IssueType.STRUCTURE,element.line(),element.col(),path,we != null,"String_Node_Str" + ref + "String_Node_Str");
  }
  if (we != null && pol.checkType()) {
    if (warning(errors,IssueType.STRUCTURE,element.line(),element.col(),path,ft != null,"String_Node_Str")) {
      boolean ok=false;
      CommaSeparatedStringBuilder b=new CommaSeparatedStringBuilder();
      for (      TypeRefComponent type : container.getType()) {
        if (!ok && type.getCode().equals("String_Node_Str")) {
          if (!type.hasTargetProfile() || type.getTargetProfile().equals("String_Node_Str"))           ok=true;
 else {
            String pr=type.getTargetProfile();
            String bt=getBaseType(profile,pr);
            StructureDefinition sd=context.fetchResource(StructureDefinition.class,"String_Node_Str" + bt);
            if (rule(errors,IssueType.STRUCTURE,element.line(),element.col(),path,bt != null,"String_Node_Str" + pr + "String_Node_Str")) {
              b.append(bt);
              ok=bt.equals(ft);
              if (ok && we != null && pol.checkValid()) {
                doResourceProfile(appContext,we,pr,errors,stack.push(we,-1,null,null),path,element);
              }
            }
 else             ok=true;
            if (ok && type.hasAggregation()) {
              boolean modeOk;
              for (              Enumeration<AggregationMode> mode : type.getAggregation()) {
                if (mode.getValue().equals(AggregationMode.CONTAINED) && refType.equals("String_Node_Str"))                 ok=true;
 else                 if (mode.getValue().equals(AggregationMode.BUNDLED) && refType.equals("String_Node_Str"))                 ok=true;
 else                 if (mode.getValue().equals(AggregationMode.REFERENCED) && (refType.equals("String_Node_Str") || refType.equals("String_Node_Str")))                 ok=true;
              }
              rule(errors,IssueType.STRUCTURE,element.line(),element.col(),path,ok,"String_Node_Str" + refType + "String_Node_Str");
            }
          }
        }
        if (!ok && type.getCode().equals("String_Node_Str")) {
          ok=true;
        }
      }
      rule(errors,IssueType.STRUCTURE,element.line(),element.col(),path,ok,"String_Node_Str" + ft + "String_Node_Str"+ b.toString()+ "String_Node_Str");
    }
  }
  if (pol == ReferenceValidationPolicy.CHECK_VALID) {
  }
}

Fixed version (ground truth):
private void checkReference(Object appContext,List<ValidationMessage> errors,String path,Element element,StructureDefinition profile,ElementDefinition container,String parentType,NodeStack stack) throws FHIRException, IOException {
  String ref=null;
  try {
    ref=element.getNamedChildValue("String_Node_Str");
  }
 catch (  Error e) {
  }
  if (Utilities.noString(ref)) {
    warning(errors,IssueType.STRUCTURE,element.line(),element.col(),path,!Utilities.noString(element.getNamedChildValue("String_Node_Str")),"String_Node_Str");
    return;
  }
  Element we=localResolve(ref,stack,errors,path);
  String refType;
  if (ref.startsWith("String_Node_Str")) {
    refType="String_Node_Str";
  }
 else {
    if (we == null) {
      refType="String_Node_Str";
    }
 else {
      refType="String_Node_Str";
    }
  }
  String ft;
  if (we != null)   ft=we.getType();
 else   ft=tryParse(ref);
  ReferenceValidationPolicy pol=refType.equals("String_Node_Str") ? ReferenceValidationPolicy.CHECK_VALID : fetcher == null ? ReferenceValidationPolicy.IGNORE : fetcher.validationPolicy(appContext,path,ref);
  if (pol.checkExists()) {
    if (we == null) {
      if (fetcher == null)       throw new FHIRException("String_Node_Str");
      we=fetcher.fetch(appContext,ref);
    }
    rule(errors,IssueType.STRUCTURE,element.line(),element.col(),path,we != null,"String_Node_Str" + ref + "String_Node_Str");
  }
  if (we != null && pol.checkType()) {
    if (warning(errors,IssueType.STRUCTURE,element.line(),element.col(),path,ft != null,"String_Node_Str")) {
      boolean ok=false;
      CommaSeparatedStringBuilder b=new CommaSeparatedStringBuilder();
      for (      TypeRefComponent type : container.getType()) {
        if (!ok && type.getCode().equals("String_Node_Str")) {
          if (!type.hasTargetProfile() || type.getTargetProfile().equals("String_Node_Str"))           ok=true;
 else {
            String pr=type.getTargetProfile();
            String bt=getBaseType(profile,pr);
            StructureDefinition sd=context.fetchResource(StructureDefinition.class,"String_Node_Str" + bt);
            if (rule(errors,IssueType.STRUCTURE,element.line(),element.col(),path,bt != null,"String_Node_Str" + pr + "String_Node_Str")) {
              b.append(bt);
              ok=bt.equals(ft);
              if (ok && we != null && pol.checkValid()) {
                doResourceProfile(appContext,we,pr,errors,stack.push(we,-1,null,null),path,element);
              }
            }
 else             ok=true;
            if (ok && type.hasAggregation()) {
              boolean modeOk;
              for (              Enumeration<AggregationMode> mode : type.getAggregation()) {
                if (mode.getValue().equals(AggregationMode.CONTAINED) && refType.equals("String_Node_Str"))                 ok=true;
 else                 if (mode.getValue().equals(AggregationMode.BUNDLED) && refType.equals("String_Node_Str"))                 ok=true;
 else                 if (mode.getValue().equals(AggregationMode.REFERENCED) && (refType.equals("String_Node_Str") || refType.equals("String_Node_Str")))                 ok=true;
              }
              rule(errors,IssueType.STRUCTURE,element.line(),element.col(),path,ok,"String_Node_Str" + refType + "String_Node_Str");
            }
          }
        }
        if (!ok && type.getCode().equals("String_Node_Str")) {
          ok=true;
        }
      }
      rule(errors,IssueType.STRUCTURE,element.line(),element.col(),path,ok,"String_Node_Str" + ft + "String_Node_Str"+ b.toString()+ "String_Node_Str");
    }
  }
  if (pol == ReferenceValidationPolicy.CHECK_VALID) {
  }
}