-Ycheck failure for inline accessors generated in packages

[nicolasstucki]

Compiler version

3.4.0-RC3 (probably also on 3.3.X)

Minimized code

package foo
package object G:
  private[foo] val valBinaryAPI2: Int = 1
package object H:
  inline def inlined = G.valBinaryAPI2 // -Ycheck failure

or

package foo
package I:
  private[foo] val valBinaryAPI2: Int = 1
package J:
  inline def inlined = I.valBinaryAPI2 // -Ycheck failure

Output

[[syntax trees at end of                     typer]] // tests/neg/inline-unstable-accessors.scala
package foo {
  package foo.G {
    final lazy module val package: foo.G.package = new foo.G.package()
    final module class package() extends Object() { this: foo.G.package.type =>
      private[foo] val valBinaryAPI2: Int = 1
    }
  }
  package foo.H {
    final lazy module val package: foo.H.package = new foo.H.package()
    final module class package() extends Object() { this: foo.H.package.type =>
      inline def inlined: Int = foo.H.inline$valBinaryAPI2$i1(foo.G):Int
      def inline$valBinaryAPI2$i1(x$0: foo.G): Int = x$0.valBinaryAPI2
    }
  }
}

checking tests/neg/inline-unstable-accessors.scala after phase MegaPhase{crossVersionChecks, firstTransform, checkReentrant, elimPackagePrefixes, cookComments, checkLoopingImplicits, betaReduce, inlineVals, expandSAMs, elimRepeated, refchecks}

  exception while retyping def inline$valBinaryAPI2$i1(x$0: foo.G): Int = x$0.valBinaryAPI2 of class DefDef # -1

  An unhandled exception was thrown in the compiler.
  Please file a crash report here:
  https://github.com/lampepfl/dotty/issues/new/choose
  For non-enriched exceptions, compile with -Yno-enrich-error-messages.

     while compiling: tests/neg/inline-unstable-accessors.scala
        during phase: Ycheck
                mode: Mode(ImplicitsEnabled)
     library version: version 2.13.12
    compiler version: version 3.4.1-RC1-bin-SNAPSHOT-nonbootstrapped-git-c48406c
            settings: -Ycheck List(all) -classpath /Users/nicolasstucki/Library/Caches/Coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala-library/2.13.12/scala-library-2.13.12.jar:/Users/nicolasstucki/Github/dotty/library/../out/bootstrap/scala3-library-bootstrapped/scala-3.4.1-RC1-bin-SNAPSHOT-nonbootstrapped/scala3-library_3-3.4.1-RC1-bin-SNAPSHOT.jar -d /
Exception in thread "main" *** error while checking tests/neg/inline-unstable-accessors.scala after phase MegaPhase{crossVersionChecks, firstTransform, checkReentrant, elimPackagePrefixes, cookComments, checkLoopingImplicits, betaReduce, inlineVals, expandSAMs, elimRepeated, refchecks} ***
java.lang.AssertionError: assertion failed: non member selection of value valBinaryAPI2 in package foo.G from (x$0 : foo.G) in x$0.valBinaryAPI2
        at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
        at dotty.tools.dotc.transform.FirstTransform.checkPostCondition(FirstTransform.scala:62)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted$$anonfun$1(TreeChecker.scala:415)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.immutable.List.foreach(List.scala:333)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:415)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:381)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3389)
        at dotty.tools.dotc.typer.Typer.$anonfun$62(Typer.scala:2601)
        at dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:256)
        at dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:2601)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedDefDef$$anonfun$1(TreeChecker.scala:611)
        at dotty.tools.dotc.transform.TreeChecker$Checker.withDefinedSyms(TreeChecker.scala:248)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedDefDef(TreeChecker.scala:614)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3095)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3196)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:398)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:381)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3300)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3346)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:654)
        at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2788)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedClassDef(TreeChecker.scala:581)
        at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3101)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3105)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3196)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:398)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:381)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3300)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3346)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:654)
        at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2921)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedPackageDef(TreeChecker.scala:680)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3147)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3197)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:398)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:381)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3327)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3346)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:654)
        at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2921)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedPackageDef(TreeChecker.scala:680)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3147)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3197)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:398)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:381)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3389)
        at dotty.tools.dotc.transform.TreeChecker.check(TreeChecker.scala:129)
        at dotty.tools.dotc.transform.TreeChecker.run(TreeChecker.scala:109)
        at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:354)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.immutable.List.foreach(List.scala:333)
        at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:360)
        at dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:315)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
        at dotty.tools.dotc.Run.runPhases$1(Run.scala:337)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:350)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:359)
        at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:69)
        at dotty.tools.dotc.Run.compileUnits(Run.scala:359)
        at dotty.tools.dotc.Run.compileSources(Run.scala:261)
        at dotty.tools.dotc.Run.compile(Run.scala:246)
        at dotty.tools.dotc.Driver.doCompile(Driver.scala:37)
        at dotty.tools.dotc.Driver.process(Driver.scala:197)
        at dotty.tools.dotc.Driver.process(Driver.scala:165)
        at dotty.tools.dotc.Driver.process(Driver.scala:177)
        at dotty.tools.dotc.Driver.main(Driver.scala:207)
        at dotty.tools.dotc.Main.main(Main.scala)

Expectation

It should pass -Ycheck or emit an error if it is impossible to generate such accessor.

[nicolasstucki]

Also see #19245 (comment)

[nicolasstucki]

      def inline$valBinaryAPI2$i1(x$0: foo.G): Int = x$0.valBinaryAPI2

should probably not receive foo.G as a parameter as it is statically known. We should probably generate

      def inline$valBinaryAPI2$i1: Int = foo.G.valBinaryAPI2

Unfortunately, this is a binary incompatible change. We will need to wait until -WunstableInlineAccessors is settled and we allow breaking changes in the in auto-generated inline accessors.