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The Scala 3 compiler, also known as Dotty.
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cyclic reference crash with `-from-tasty` with parents/params loop #12872

Open bishabosha opened 3 years ago

bishabosha commented 3 years ago

Compiler Version

3.0.2-RC1

Minimized code

I can now make a cyclic reference crash when compiling -from-tasty with this augmented example to tests/pos/i12834.scala

class C(val d: D, val ref: Option[d.Type])
class D extends C(null, None) {
  type Type
}
```scala Exception in thread "main" java.lang.AssertionError: assertion failed: Cyclic reference while unpickling definition at address 47 in unit tests/pos/i12834.scala at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedDef(TreeUnpickler.scala:770) at dotty.tools.dotc.core.tasty.TreeUnpickler$Completer.complete(TreeUnpickler.scala:122) at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:167) at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:188) at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:190) at dotty.tools.dotc.core.Denotations$SingleDenotation.signature(Denotations.scala:610) at dotty.tools.dotc.core.Denotations$SingleDenotation.signature(Denotations.scala:602) at dotty.tools.dotc.core.Denotations$SingleDenotation.atSignature(Denotations.scala:644) at dotty.tools.dotc.core.Denotations$SingleDenotation.atSignature(Denotations.scala:642) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readLengthTerm$1(TreeUnpickler.scala:1223) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTerm(TreeUnpickler.scala:1297) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readLengthTerm$1(TreeUnpickler.scala:1137) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTerm(TreeUnpickler.scala:1297) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.$anonfun$4(TreeUnpickler.scala:932) at dotty.tools.tasty.TastyReader.collectWhile(TastyReader.scala:137) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTemplate(TreeUnpickler.scala:935) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readNewDef(TreeUnpickler.scala:857) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedDef(TreeUnpickler.scala:776) at dotty.tools.dotc.core.tasty.TreeUnpickler$Completer.complete(TreeUnpickler.scala:122) at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:167) at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:188) at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:190) at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:188) at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:190) at dotty.tools.dotc.core.SymDenotations$ClassDenotation.computeMembersNamed(SymDenotations.scala:2030) at dotty.tools.dotc.core.SymDenotations$ClassDenotation.membersNamed(SymDenotations.scala:2000) at dotty.tools.dotc.core.SymDenotations$ClassDenotation.findMember(SymDenotations.scala:2051) at dotty.tools.dotc.core.Types$Type.go$1(Types.scala:683) at dotty.tools.dotc.core.Types$Type.findMember(Types.scala:870) at dotty.tools.dotc.core.tasty.TreeUnpickler.dotty$tools$dotc$core$tasty$TreeUnpickler$TreeReader$$_$accessibleDenot$1(TreeUnpickler.scala:1091) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.completeSelect$1(TreeUnpickler.scala:1082) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readSimpleTerm$1(TreeUnpickler.scala:1110) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTerm(TreeUnpickler.scala:1297) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTpt(TreeUnpickler.scala:1327) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.$anonfun$27(TreeUnpickler.scala:1263) at dotty.tools.tasty.TastyReader.until(TastyReader.scala:125) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readLengthTerm$1(TreeUnpickler.scala:1263) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTerm(TreeUnpickler.scala:1297) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTpt(TreeUnpickler.scala:1327) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readNewDef(TreeUnpickler.scala:875) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedDef(TreeUnpickler.scala:776) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedParams$$anonfun$2(TreeUnpickler.scala:1042) at dotty.tools.tasty.TastyReader.collectWhile(TastyReader.scala:137) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedParams(TreeUnpickler.scala:1042) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readParams(TreeUnpickler.scala:1047) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readParamss$1(TreeUnpickler.scala:794) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readNewDef(TreeUnpickler.scala:830) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedDef(TreeUnpickler.scala:776) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTemplate(TreeUnpickler.scala:948) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readNewDef(TreeUnpickler.scala:857) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedDef(TreeUnpickler.scala:776) ```

before https://github.com/lampepfl/dotty/pull/12844 this code would create the same error as #12834

Originally posted by @bishabosha in https://github.com/lampepfl/dotty/issues/12844#issuecomment-863906113

odersky commented 3 years ago

This looks pretty hard to fix. What happens is:

One way to fix this would be to carefully analyze what Namer does in this case (it's not pretty!) and duplicate the same behavior in TreeUnpickler. But I don't have the bandwidth to do this right now, so it would be good is someone else could take a look. @bishabosha can you try, or find somebody else to take this on?

nicolasstucki commented 2 years ago

Can be reproduced with scalac -Ytest-pickler

KacperFKorban commented 2 years ago

I found a very similar issue recently when trying to migrate scala.rx to Scala 3.

Reproduction:

// _1.scala
class Ctx(rx0: Ctx.Owner)

object Ctx {
  class Owner() extends Ctx(???)
}
// _2.scala
def test = {
  Ctx.Owner
}

Crash msg:

```scala java.lang.AssertionError: assertion failed: Cyclic reference while unpickling definition at address 35 in unit main.scala while compiling Ctx.tasty Exception in thread "main" java.lang.AssertionError: assertion failed: Cyclic reference while unpickling definition at address 35 in unit main.scala at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedDef(TreeUnpickler.scala:796) at dotty.tools.dotc.core.tasty.TreeUnpickler$Completer.liftedTree1$1(TreeUnpickler.scala:133) at dotty.tools.dotc.core.tasty.TreeUnpickler$Completer.complete(TreeUnpickler.scala:137) at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:171) at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:187) at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:189) at dotty.tools.dotc.core.Denotations$SingleDenotation.signature(Denotations.scala:613) at dotty.tools.dotc.core.Denotations$SingleDenotation.signature(Denotations.scala:605) at dotty.tools.dotc.core.Denotations$SingleDenotation.atSignature(Denotations.scala:647) at dotty.tools.dotc.core.Denotations$SingleDenotation.atSignature(Denotations.scala:645) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readLengthTerm$1(TreeUnpickler.scala:1299) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTerm(TreeUnpickler.scala:1373) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readLengthTerm$1(TreeUnpickler.scala:1210) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTerm(TreeUnpickler.scala:1373) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.$anonfun$19(TreeUnpickler.scala:962) at dotty.tools.tasty.TastyReader.collectWhile(TastyReader.scala:137) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTemplate(TreeUnpickler.scala:965) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readNewDef(TreeUnpickler.scala:883) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedDef(TreeUnpickler.scala:802) at dotty.tools.dotc.core.tasty.TreeUnpickler$Completer.liftedTree1$1(TreeUnpickler.scala:133) at dotty.tools.dotc.core.tasty.TreeUnpickler$Completer.complete(TreeUnpickler.scala:137) at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:171) at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:187) at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:189) at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:373) at dotty.tools.dotc.core.SymDenotations$SymDenotation.annotations(SymDenotations.scala:228) at dotty.tools.dotc.core.SymDenotations$SymDenotation.getAnnotation(SymDenotations.scala:249) at dotty.tools.dotc.core.SymDenotations$SymDenotation.targetName(SymDenotations.scala:530) at dotty.tools.dotc.core.SymDenotations$SymDenotation.hasTargetName(SymDenotations.scala:520) at dotty.tools.dotc.core.Denotations$SingleDenotation.atSignature(Denotations.scala:657) at dotty.tools.dotc.core.Denotations$SingleDenotation.atSignature(Denotations.scala:645) at dotty.tools.dotc.core.tasty.TreeUnpickler.dotty$tools$dotc$core$tasty$TreeUnpickler$TreeReader$$_$accessibleDenot$1(TreeUnpickler.scala:1130) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.completeSelect$1(TreeUnpickler.scala:1121) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readSimpleTerm$1(TreeUnpickler.scala:1149) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTerm(TreeUnpickler.scala:1373) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTpt(TreeUnpickler.scala:1401) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readNewDef(TreeUnpickler.scala:911) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedDef(TreeUnpickler.scala:802) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedParams$$anonfun$2(TreeUnpickler.scala:1083) at dotty.tools.tasty.TastyReader.collectWhile(TastyReader.scala:137) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedParams(TreeUnpickler.scala:1083) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readParams(TreeUnpickler.scala:1088) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readParamss$1(TreeUnpickler.scala:820) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readNewDef(TreeUnpickler.scala:856) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedDef(TreeUnpickler.scala:802) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTemplate(TreeUnpickler.scala:978) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readNewDef(TreeUnpickler.scala:883) at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedDef(TreeUnpickler.scala:802) at dotty.tools.dotc.core.tasty.TreeUnpickler$Completer.liftedTree1$1(TreeUnpickler.scala:133) at dotty.tools.dotc.core.tasty.TreeUnpickler$Completer.complete(TreeUnpickler.scala:137) at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:171) at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:187) at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:189) at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:373) at dotty.tools.dotc.core.Symbols$ClassSymbol.rootTreeContaining(Symbols.scala:396) at dotty.tools.dotc.core.Symbols$ClassSymbol.rootTree(Symbols.scala:387) at dotty.tools.dotc.fromtasty.ReadTasty.compilationUnit$1(ReadTasty.scala:40) at dotty.tools.dotc.fromtasty.ReadTasty.readTASTY(ReadTasty.scala:70) at dotty.tools.dotc.fromtasty.ReadTasty.runOn$$anonfun$1(ReadTasty.scala:25) at scala.collection.immutable.List.flatMap(List.scala:293) at dotty.tools.dotc.fromtasty.ReadTasty.runOn(ReadTasty.scala:25) at dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:234) at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15) at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10) at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1328) at dotty.tools.dotc.Run.runPhases$1(Run.scala:245) at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:253) at dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:262) at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:68) at dotty.tools.dotc.Run.compileUnits(Run.scala:262) at dotty.tools.dotc.Run.compileUnits(Run.scala:192) at dotty.tools.dotc.fromtasty.TASTYRun.compile(TASTYRun.scala:14) at dotty.tools.dotc.Driver.doCompile(Driver.scala:35) at dotty.tools.dotc.Driver.process(Driver.scala:195) at dotty.tools.dotc.Driver.process(Driver.scala:163) at dotty.tools.dotc.Driver.process(Driver.scala:175) at dotty.tools.dotc.Driver.main(Driver.scala:205) at dotty.tools.MainGenericCompiler$.run$1(MainGenericCompiler.scala:162) at dotty.tools.MainGenericCompiler$.main(MainGenericCompiler.scala:186) at dotty.tools.MainGenericCompiler.main(MainGenericCompiler.scala) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at coursier.bootstrap.launcher.a.a(Unknown Source) at coursier.bootstrap.launcher.Launcher.main(Unknown Source) ```

The difference here is that it crashed the compiler ever since 3.0.0 (and probably earlier).

The weird thing is also that the following code compiles correctly: (Owner and Ctx are put in different .tasty files)

// _1.scala
class Ctx(rx0: Ctx.Owner)

class Owner() extends Ctx(???)

Details

The situation here seems to be similar to what @odersky described.

  1. Try to unpickle object Ctx
  2. Try to unpickle class Owner (requires its parents -> class Ctx)
  3. Try to unpickle class Ctx (requires params of it's constructor -> class Owner)
  4. Try to unpickle class Owner -> Cyclic reference error.