Cannot $inc positional array while performing $setOnInsert operation

If one tries to $setOnInsert an array or increment a positional (or several) elements of that array if that document already exists, the instruction fails. Depending on the order by which they are placed on the update statement it resolves 2 different error messages:

• $setOnInsert before $inc

  db.t.update({_id:'12345',hour:12345},{ $setOnInsert: { rpm: [10, 15] }, $inc: { count: 1, 'rpm.$0': 10, 'rpm.$1': 15 }}, { upsert:true })

  WriteResult({

  "nMatched" : 0,

  "nUpserted" : 0,

  "nModified" : 0,

  "writeError" : {

  "code" : 16836,

  "errmsg" : "cannot use the part (rpm of rpm.$0) to traverse the element ({rpm: [ 10.0, 15.0 ]})"

  }

  })

• $seOnInsert after $inc

  db.t.update({_id:'12345',hour:12345},{ $inc: { count: 1, 'rpm.$0': 10, 'rpm.$1': 15 }, $setOnInsert: { rpm: [10, 15] }}, { upsert:true })

  WriteResult({

  "nMatched" : 0,

  "nUpserted" : 0,

  "nModified" : 0,

  "writeError" : {

  "code" : 16836,

  "errmsg" : "Cannot update 'rpm.$0' and 'rpm' at the same time"

  }

  })

In either situation this operation should be valid since it's very common, specially for time series operations/use cases, where we need to preallocate arrays and increment counters if those already exist.

The code reveals that we do not treat this valid situation:
https://github.com/mongodb/mongo/blob/master/src/mongo/db/ops/path_support.cpp#L110

https://github.com/mongodb/mongo/blob/master/src/mongo/db/ops/update_driver.cpp#L270-L278