Method overload in trait + default parameter values causes compiler crash

[antognini]

Compiler version

3.3.0

Minimized code

trait A:
  def foo = 1
  def foo(x: Int = 0) = 2

val a = new A{}
a.foo
a.foo()

(new A{}).foo
(new A{}).foo() // compiler crashes at this line

Output (click arrow to expand)

java.util.NoSuchElementException: None.get
scala.None$.get(Option.scala:627)
scala.None$.get(Option.scala:626)
dotty.tools.dotc.transform.LambdaLift.transformTemplate(LambdaLift.scala:336)
dotty.tools.dotc.transform.LambdaLift.transformTemplate(LambdaLift.scala:332)
dotty.tools.dotc.transform.MegaPhase.goTemplate(MegaPhase.scala:1010)
dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:360)
dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:427)
dotty.tools.dotc.transform.MegaPhase.transformNamed$1(MegaPhase.scala:255)
dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:425)
dotty.tools.dotc.transform.MegaPhase.loop$2(MegaPhase.scala:444)
dotty.tools.dotc.transform.MegaPhase.transformBlock(MegaPhase.scala:449)

Expectation

The code should compile

[mbovel]

As #17581 has been fixed, I suggest the team @dwijnand, @eugenefle, @hamzaremmal, @iusildra switches to this issue for tomorrow's Dotty Spree.

[dwijnand]

This has nothing to do with overloading (as it looked) but only about default arguments. We couldn't figure out exactly how LambdaLift works, but clearly it didn't expect the duplication that derives from a default argument, so it crashes like it does.