Generated jsonFormatN has unexpectedly large sizeHint

[cplesner-humio]

The code generated for this line,

spray-json/src/main/boilerplate/spray/json/ProductFormatsInstances.scala.template

Line 31 in d0008f5

fields.sizeHint(1 * 2)

is expanded to this for instance for jsonFormat21:

    def write(p: T) = {
      val fields = new collection.mutable.ListBuffer[(String, JsValue)]
      fields.sizeHint(20 * 21)
      fields ++= productElement2Field[P1](fieldName1, p, 0)
      ...

I don't think ListBuffer actually uses the size hint so it's not that bad but if you ever switched to a different kind of collection that did (and actually side note: why not use Map.newBuilder instead?) it would be quite problematic.

[jrudolph]

Agreed, the whole setup is quite weird.