Shared via Pony Playground (https://playground.ponylang.io/?gist=061d51b5b09d813ef31fa3650d95cca7)

main.pony

trait SomeTrait
	fun tag getVal() : U32 =>

		2


class SomeClass


class Some is SomeTrait

	// works, if ` = SomeClass` is uncommented:
	embed eClass : SomeClass // = SomeClass

	new create( env' : Env) =>

		// // works, if line below is uncommented:
		// eClass = SomeClass

		getVal()

		// doesnt work, if line below is uncommented:
		eClass = SomeClass


actor Main
	new create( e' : Env) =>
		e'