I have a gears library, depending on
"org.typelevel" %% "cats-core" % "2.7.0",
"org.typelevel" %% "cats-effect" % "2.5.4"
cats-effect 2.5.4 depends on cats-core 2.6.1, so the latter is evicted. I'm not sure this matters though.
This library is used by a few services. In the gears library there is StreamMetrics trait used by main (runnable) class of all of them. It contains following piece of code:
implicit val traverseMeasured: Traverse[Measured] = new Traverse[Measured] { ... }
In some (but not all) services I get following error when I try to start them (I added newlines):
java.lang.AbstractMethodError: Receiver class my.company.platform.image.MainModule$$anon$9
does not define or inherit an implementation of the resolved method
'abstract void my$company$gear$metrics$StreamMetrics$_setter_$traverseMeasured_$eq(cats.Traverse)'
of interface my.company.gear.metrics.StreamMetrics.
From my understanding the my$company$gear$metrics$StreamMetrics$_setter_$traverseMeasured_$eq(cats.Traverse) is setter generated by scala compiler for implicit val traverseMeasured. This setter is defined and obviously used only in StreamMetrics trait - it's val so I can't set it anywhere else. So why the error?