Reproduction steps

Scala version: 2.13.13

The issue is reproducible only on scala 2.13.13, because a recent patch to the ArrayBuilder triggered it, but the incriminated code is probably the same in every scala release: https://github.com/scala/scala/blob/5aa3dc5ea77800ddd2a3bdf9e7feeea57484421c/src/library/scala/collection/mutable/ArrayBuffer.scala#L326-L331

As you can see from the code above, if the targetLen is 0 the array length is doubled.

Here you can find a minimal test-case: https://github.com/alexdupre/scala-2.13.13-bug

Just sbt run to reproduce it.

Problem

OutOfMemoryError because the underlying array is doubled at every iteration even if no elements have been added.