Names of vals or vars may not end in _=, said scalac.

[som-snytt]

Minimized code

class C:
  var __= : Int = 42      // or similar val x_=

Output (click arrow to expand)

exception occurred while compiling badvar.scala
java.util.NoSuchElementException: head of empty list while compiling badvar.scala
Exception in thread "main" java.util.NoSuchElementException: head of empty list
	at scala.collection.immutable.Nil$.head(List.scala:629)
	at scala.collection.immutable.Nil$.head(List.scala:628)
	at dotty.tools.dotc.transform.Memoize.newField$1(Memoize.scala:78)
	at dotty.tools.dotc.transform.Memoize.$anonfun$1(Memoize.scala:118)
	at dotty.tools.dotc.core.Symbols$Symbol.orElse(Symbols.scala:617)
	at dotty.tools.dotc.transform.Memoize.transformDefDef(Memoize.scala:118)
	at dotty.tools.dotc.transform.MegaPhase.goDefDef(MegaPhase.scala:941)
	at dotty.tools.dotc.transform.MegaPhase.goDefDef(MegaPhase.scala:942)
	at dotty.tools.dotc.transform.MegaPhase.goDefDef(MegaPhase.scala:942)
	at dotty.tools.dotc.transform.MegaPhase.transformNamed$1(MegaPhase.scala:248)
	at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:394)
	at dotty.tools.dotc.transform.MegaPhase.transformStat$2(MegaPhase.scala:404)
	at dotty.tools.dotc.transform.MegaPhase.$anonfun$1(MegaPhase.scala:409)
	at scala.collection.immutable.List.mapConserve(List.scala:472)
	at dotty.tools.dotc.transform.MegaPhase.transformStats(MegaPhase.scala:409)
	at dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:339)
	at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:396)
	at dotty.tools.dotc.transform.MegaPhase.transformNamed$1(MegaPhase.scala:251)
	at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:394)
	at dotty.tools.dotc.transform.MegaPhase.transformStat$2(MegaPhase.scala:404)
	at dotty.tools.dotc.transform.MegaPhase.$anonfun$1(MegaPhase.scala:409)
	at scala.collection.immutable.List.mapConserve(List.scala:472)
	at dotty.tools.dotc.transform.MegaPhase.transformStats(MegaPhase.scala:409)
	at dotty.tools.dotc.transform.MegaPhase.mapPackage$1(MegaPhase.scala:356)
	at dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:359)
	at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:396)
	at dotty.tools.dotc.transform.MegaPhase.transformUnit(MegaPhase.scala:415)
	at dotty.tools.dotc.transform.MegaPhase.run(MegaPhase.scala:427)
	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:318)
	at scala.collection.immutable.List.map(List.scala:246)
	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:319)
	at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:165)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
	at dotty.tools.dotc.Run.runPhases$5(Run.scala:175)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:183)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:64)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:190)
	at dotty.tools.dotc.Run.compileSources(Run.scala:127)
	at dotty.tools.dotc.Run.compile(Run.scala:110)
	at dotty.tools.dotc.Driver.doCompile(Driver.scala:38)
	at dotty.tools.dotc.Driver.process(Driver.scala:194)
	at dotty.tools.dotc.Driver.process(Driver.scala:163)
	at dotty.tools.dotc.Driver.process(Driver.scala:175)
	at dotty.tools.dotc.Driver.main(Driver.scala:202)
	at dotty.tools.dotc.Main.main(Main.scala)

[som-snytt]

What's missing is Dotty merchandise that says MegaPhase.

A t-shirt with a comics panel in which our hero, faced with an overwhelming alien force, cries out in a speech balloon: transform.MegaPhase! to activate their superpowers.