StackOverflowError in TypeReprStructure printer for structural type with type member

[TomasMikula]

Compiler version

3.6.3

Minimized code

defs.scala

import scala.quoted.*

type Structural = {
  type T
  def make: T
}

transparent inline def go =
  ${ goImpl }

private def goImpl(using Quotes): Expr[Any] = {
  import quotes.reflect.{*, given}

  val t = '{
    new AnyRef {
      opaque type T = Int
      def make: T = 0
    } : Structural
  }

  val tpe = t.asTerm.tpe

  println(Printer.TypeReprCode.show(tpe))   // OK

  try {
    Printer.TypeReprStructure.show(tpe) // StackOverflowError
  } catch {
    case e: StackOverflowError =>
      e.printStackTrace
  }

  Expr("hello")
}

test.scala

val x = go

Output

% ~/Downloads/scala3-3.6.3-aarch64-apple-darwin/bin/scalac defs.scala test.scala
java.lang.Object {
  type T >: scala.Nothing <: scala.Any
  def make: this.<none>
}
java.lang.StackOverflowError
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:201)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter$TypeOps.$plus$eq(Extractors.scala:303)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:207)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter$TypeOps.$plus$eq(Extractors.scala:303)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:209)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter$TypeOps.$plus$eq(Extractors.scala:303)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:209)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter$TypeOps.$plus$eq(Extractors.scala:303)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:231)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter$TypeOps.$plus$eq(Extractors.scala:303)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:229)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter$TypeOps.$plus$eq(Extractors.scala:303)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:207)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter$TypeOps.$plus$eq(Extractors.scala:303)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:221)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter$TypeOps.$plus$eq(Extractors.scala:303)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:209)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter$TypeOps.$plus$eq(Extractors.scala:303)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:231)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter$TypeOps.$plus$eq(Extractors.scala:303)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:229)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter$TypeOps.$plus$eq(Extractors.scala:303)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:207)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter$TypeOps.$plus$eq(Extractors.scala:303)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:221)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter$TypeOps.$plus$eq(Extractors.scala:303)
	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:209)

[TomasMikula]

Here's a shorter reproduction (but does not print the stack trace):

macro.scala

import scala.quoted.*

inline def structureOf[T]: String =
  ${ structureOfImpl[T] }

private def structureOfImpl[T](using Quotes, Type[T]): Expr[String] =
  import quotes.reflect.*
  val str = Printer.TypeReprStructure.show(TypeRepr.of[T])
  Expr(str)

test.scala

@main def test =
  structureOf[{
    type T
    def make: T
  }]

Output

% ~/Downloads/scala3-3.6.4-aarch64-apple-darwin/bin/scalac macro.scala test.scala
-- Error: test.scala:2:13 ------------------------------------------------------
2 |  structureOf[{
  |  ^
  |  Exception occurred while executing macro expansion.
  |  java.lang.StackOverflowError
  |
3 |    type T
4 |    def make: T
5 |  }]
  |-----------------------------------------------------------------------------
  |Inline stack trace
  |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  |This location contains code that was inlined from macro.scala:4
4 |  ${ structureOfImpl[T] }
  |  ^^^^^^^^^^^^^^^^^^^^^^^
   -----------------------------------------------------------------------------
1 error found