I understand that the function 'updateTracker' is not accepting arguments of type struct array during code generation.
Since C/C++ are statically typed languages, the fields, their types and sizes of the structure variables/arguments should be known at compile time for code generation to succeed.
In your case, the fields of the structure you are passing into the function is unknown at compile time, since it is dependent on the output of the 'clusterDetections' function that is known at run time.
If the fields of the structure is known and do not change, try predefining the variable 'detectionClusters' as an struct array and pass it as an argument into the function 'updateTracker'.
The following documentation page gives more insights on implementing the same.
Hope this helps.