Assertion fail in dotty.tools.dotc.core.TypeOps$.dominators$1(TypeOps.scala:248) using Coulomb+Sourcecode libs

[benhutchison]

Compiler version

3.3.0-RC3

Minimized code

I minimized what I'm seeing locally in a project down to this Scastie:
https://scastie.scala-lang.org/7QFQRDLcQBua2DedfMeUzQ

The code requires Coulomb and Sourcecode libraries to exhibit the error. Coulomb's opaque type Quantity[V, U] needs to be used, and the library needs to be exposed via export for the error to happen.

import cats.*
import cats.data.*
import cats.syntax.all.*

import sourcecode.{*, given}

object Exports:
  export coulomb.{Quantity, DeltaQuantity, /, `*`, ^}
  export coulomb.syntax.{withUnit, withDeltaUnit}
  object allalgebra extends algebra.instances.AllInstances
  export allalgebra.{*, given}
  export coulomb.ops.algebra.spire.all.{*, given}
  export coulomb.policy.spire.standard.given
  export coulomb.conversion.{UnitConversion, TruncatingUnitConversion}

import Exports.{given, *}

type EitherNecs[T] = EitherNec[String, T]

object Valid:
  def validateQtyGTE[T, V: Order, U](n: Text[Quantity[V, U]], threshold: Text[Quantity[V, U]], context: =>String = "", target: T = ()): EitherNecs[T] =
    if (n.value < threshold.value) then s"Invalid:$context ${n.source}=${n.value} <= ${threshold.source}=${threshold.value}".leftNec
    else target.rightNec

Valid.validateQtyGTE(1.withUnit[Unit], 0.withUnit[Unit])

println("done")

Locally I see an assertion fail at:

[error] java.lang.AssertionError: assertion failed
[error] scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:11)
[error] dotty.tools.dotc.core.TypeOps$.dominators$1(TypeOps.scala:248)
[error] dotty.tools.dotc.core.TypeOps$.approximateOr$1(TypeOps.scala:382)
[error] dotty.tools.dotc.core.TypeOps$.orDominator(TypeOps.scala:395)
[error] dotty.tools.dotc.core.TypeOps$.approximateOr$1(TypeOps.scala:363)
[error] dotty.tools.dotc.core.TypeOps$.orDominator(TypeOps.scala:395)
[error] dotty.tools.dotc.core.TypeOps$.approximateOr$1(TypeOps.scala:370)
[error] dotty.tools.dotc.core.TypeOps$.orDominator(TypeOps.scala:395)
[error] dotty.tools.dotc.core.Types$OrType.join(Types.scala:3407)
[error] dotty.tools.dotc.core.Types$Type.goOr$1(Types.scala:857)
[error] dotty.tools.dotc.core.Types$Type.go$1(Types.scala:726)
[error] dotty.tools.dotc.core.Types$Type.findMember(Types.scala:873)
..snip..

[nicolasstucki]

We need a self-contained version to reproduce it in the compiler tests.