Unability to use objects with name eq when compiled with Scala 2

[buzden]

Dotty thinks that every package compiled by Scala 2 has the eq method in it. This gives two consequences.

---

First, strange code compiles. Considering as an example, you have cats library in dependencies, you have

val z = cats.eq(new Object) // Compiles!

---

Second, all objects that have name eq in such packages, become unavailable. Considering, for example, you have cats-laws library in dependencies, this code

import cats.laws.discipline.eq._

fails with

[error] -- Error: dotty-eq-bug/src/main/scala/dottyeq/tst-pos.scala:4:28 
[error] 4 |import cats.laws.discipline.eq._
[error]   |       ^^^^^^^^^^^^^^^^^^^^^^^
[error]   |       Object => Boolean is not stable

---

This error appears both in pure dotty mode and in dotty's scala 2 compatibility mode.

---

The minimal project showing both errors can be found here.

[smarter]

Both cats and cats.laws.discipline contain a package object, and objects always have an eq method, so Dotty's behavior isn't completely unreasonable here but we should still align with Scala 2. @adriaanm do you happen to know if scalac has some logic somewhere to skip members of Any when looking into package objects ?

[adriaanm]

Don't know, sorry. I poked around a bit, but didn't see anything obvious...

[smarter]

Found it: https://github.com/scala/scala/blob/8f3a05a802aa3cc28212fc5501db31e6f1d499d6/src/reflect/scala/reflect/internal/SymbolTable.scala#L358