Unfortunately the `$name` property isn't enough with the current ODM design that led to this exception since ODM calls the class to instantiate depending on discriminator value, may be it's me who didn't give enough info about the use case, when I said "missing discriminator field value" I meant it's missing from the data being hydrated ie; ODM isn't strict about query projection in discriminated classes, however, I don't believe that either `\Doctrine\ODM\MongoDB\Query\Builder` or `\Doctrine\ODM\MongoDB\Persisters\DocumentPersister` is the right class to throw that exception at, may be we can enforce adding discriminator field to projection in the `\Doctrine\ODM\MongoDB\Query\Builder`?