Program: 11126
Project: 11126
Buggy source:
@Override public Object visitMethodExpressionTerm(@NotNull cqlParser.MethodExpressionTermContext ctx){
  FunctionRef fun=of.createFunctionRef();
  Expression left=parseExpression(ctx.expressionTerm());
  if (left instanceof IdentifierRef) {
    fun.setLibraryName(((IdentifierRef)left).getLibraryName());
    fun.setName(((IdentifierRef)left).getName());
  }
  if (ctx.expression() != null) {
    for (    cqlParser.ExpressionContext expressionContext : ctx.expression()) {
      fun.getOperand().add((Expression)visit(expressionContext));
    }
  }
  if (fun.getLibraryName() == null) {
    String ageRelatedFunctionName=resolveAgeRelatedFunction(fun.getName());
    if (ageRelatedFunctionName != null) {
switch (ageRelatedFunctionName) {
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
{
          CalculateAge operator=of.createCalculateAge().withPrecision(resolveAgeRelatedFunctionPrecision(fun.getName()));
          if (fun.getOperand().size() > 0) {
            operator.setOperand(fun.getOperand().get(0));
          }
 else {
            operator.setOperand(of.createProperty().withPath(getModelHelper().getModelInfo().getPatientBirthDatePropertyName()).withSource(of.createExpressionRef().withName("String_Node_Str")));
          }
          return operator;
        }
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
{
        CalculateAgeAt operator=of.createCalculateAgeAt().withPrecision(resolveAgeRelatedFunctionPrecision(ageRelatedFunctionName));
        operator.getOperand().addAll(fun.getOperand());
        if (operator.getOperand().size() == 1) {
          operator.getOperand().add(0,of.createProperty().withPath(getModelHelper().getModelInfo().getPatientBirthDatePropertyName()).withSource(of.createExpressionRef().withName("String_Node_Str")));
        }
        return operator;
      }
  }
}
}
return fun;
}

Fixed version (ground truth):
@Override public Object visitMethodExpressionTerm(@NotNull cqlParser.MethodExpressionTermContext ctx){
  FunctionRef fun=of.createFunctionRef();
  Expression left=parseExpression(ctx.expressionTerm());
  if (left instanceof IdentifierRef) {
    fun.setLibraryName(((IdentifierRef)left).getLibraryName());
    fun.setName(((IdentifierRef)left).getName());
  }
  if (ctx.expression() != null) {
    for (    cqlParser.ExpressionContext expressionContext : ctx.expression()) {
      fun.getOperand().add((Expression)visit(expressionContext));
    }
  }
  if (fun.getLibraryName() == null) {
    String ageRelatedFunctionName=resolveAgeRelatedFunction(fun.getName());
    if (ageRelatedFunctionName != null) {
switch (ageRelatedFunctionName) {
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
{
          CalculateAge operator=of.createCalculateAge().withPrecision(resolveAgeRelatedFunctionPrecision(ageRelatedFunctionName));
          if (fun.getOperand().size() > 0) {
            operator.setOperand(fun.getOperand().get(0));
          }
 else {
            operator.setOperand(of.createProperty().withPath(getModelHelper().getModelInfo().getPatientBirthDatePropertyName()).withSource(of.createExpressionRef().withName("String_Node_Str")));
          }
          return operator;
        }
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
case "String_Node_Str":
{
        CalculateAgeAt operator=of.createCalculateAgeAt().withPrecision(resolveAgeRelatedFunctionPrecision(ageRelatedFunctionName));
        operator.getOperand().addAll(fun.getOperand());
        if (operator.getOperand().size() == 1) {
          operator.getOperand().add(0,of.createProperty().withPath(getModelHelper().getModelInfo().getPatientBirthDatePropertyName()).withSource(of.createExpressionRef().withName("String_Node_Str")));
        }
        return operator;
      }
  }
}
}
return fun;
}