regression: Integer overflow in nesting level of a Macro expansion (PolyType/TypeBounds) between 3.1.1 and 3.1.2

Compiler version

3.1.2

Minimized code

It requires some macro magic to reproduce and I didn’t manage to extract the minimal reproducible code. But it manifests with one specific open source project https://github.com/davenverse/epimetheus

If you perform git clone and then run sbt (in my case JDK 17 was used) with these commands it will encounter compilation errors.

++ 3.1.2; Test / compile

Output

sbt log

[error] -- Error: ~/epimetheus/core/src/test/scala/io/chrisdavenport/epimetheus/CounterSpec.scala:30:68 
[error] 30 |        counter <- Counter.labelled(cr, Name("boo"), "Boo Counter", Sized(Label("foo")), {(s: String) => Sized(s)})
[error]    |                                                                    ^
[error]    |Could not decrease the nesting level of a from 2147483647 to 6 in

And a lot more of PolyType and TypeBounds output.

Expectation

Compile w/o errors like it was with 3.1.1

++ 3.1.1; Test / compile

[bishabosha]

the example still fails for me without the macro, so I removed it

[arixmkii]

I managed to minimize it to 2 Scala sources (because Macros support is involved) - Base - with macro definitions and Test with failing example. It is still big, but I eliminated all external dependencies at least.

Base.scala

package testcase

import scala.compiletime.ops.int.*

final class Label (val getLabel: String)

trait ShapelessPolyfill {

  type Represented[R] = R match {
    case IndexedSeq[a] => a
  }

  type TupleSized[R, A, N <: Int] <: Tuple = N match {
    case 0 => EmptyTuple
    case S[n] => A *: TupleSized[R, A, n]
  }

  extension [R, A, N <: Int] (s: TupleSized[R, A, N]) {
    def unsized: IndexedSeq[A] = s.productIterator.toIndexedSeq.asInstanceOf[IndexedSeq[A]]
  }

  type Nat = Int

  type Sized[Repr, L <: Nat] = TupleSized[Repr, Represented[Repr], L]

  object Sized {
    def apply[A](a1: A): Sized[IndexedSeq[A], 1] = Tuple1(a1)
  }

}

object poly extends ShapelessPolyfill

Test.scala

package testcase

import poly.*

def failing: Tuple1[Label] = Sized(new Label("foo"))

With 3.1.1 it compiles

nestingbug % ls -a                 
.		..		Base.scala	Test.scala
nestingbug % scalac -version       
Scala compiler version 3.1.1 -- Copyright 2002-2022, LAMP/EPFL
nestingbug % scalac Base.scala     
nestingbug % scalac Test.scala

With 3.1.2 it fails

nestingbug % ls -a
.		..		Base.scala	Test.scala
nestingbug % scalac -version
Scala compiler version 3.1.2 -- Copyright 2002-2022, LAMP/EPFL
nestingbug % scalac Base.scala
nestingbug % scalac Test.scala
-- Error: Test.scala:5:29 ------------------------------------------------------
5 |def failing: Tuple1[Label] = Sized(Label("foo"))
  |                             ^
  |Could not decrease the nesting level of a from 2147483647 to 2 in 
... A lot more output omitted...