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StackOverflow in the compiler #10228

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scabug opened this issue Mar 15, 2017 · 4 comments
Closed

StackOverflow in the compiler #10228

scabug opened this issue Mar 15, 2017 · 4 comments
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compiler crash
Milestone
2.13.0-RC1

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@scabug
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scabug commented Mar 15, 2017 

trait Data { self =>
  type Type >: self.type <: Data
}
trait DataF[P <: Data, A <: DataF[P, A]] extends Data { type Type = P#Type }
type Some[A <: Data] = DataF[A, A]

def g[A <: Some[A]]: Unit = {
  implicitly[A <:< A#Type]
}
@scabug
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scabug commented Mar 15, 2017

Imported From: https://issues.scala-lang.org/browse/SI-10228?orig=1
Reporter: Alexander Konovalov (alexknvl)
Affected Versions: 2.12.1

@scabug scabug added the quickfix label Apr 7, 2017
@diesalbla
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I have just reproduced the error with Scala 2.12.7. The good news is that the recursion cycle causing it is quite short:

	at scala.reflect.internal.Types.appliedType(Types.scala:3726)
	at scala.reflect.internal.Types.appliedType$(Types.scala:3725)
	at scala.reflect.internal.SymbolTable.appliedType(SymbolTable.scala:18)
	at scala.reflect.internal.tpe.TypeMaps$AsSeenFromMap.correspondingTypeArgument(TypeMaps.scala:580)
	at scala.reflect.internal.tpe.TypeMaps$AsSeenFromMap.loop$3(TypeMaps.scala:612)
	at scala.reflect.internal.tpe.TypeMaps$AsSeenFromMap.classParameterAsSeen(TypeMaps.scala:617)
	at scala.reflect.internal.tpe.TypeMaps$AsSeenFromMap.apply(TypeMaps.scala:492)
	at scala.reflect.internal.tpe.TypeMaps$TypeMap.mapOver(TypeMaps.scala:102)
	at scala.reflect.internal.tpe.TypeMaps$AsSeenFromMap.apply(TypeMaps.scala:493)
	at scala.reflect.internal.Types$Type.asSeenFrom(Types.scala:695)
	at scala.reflect.internal.Types$TypeRef.relativize(Types.scala:2173)
	at scala.reflect.internal.Types$AliasTypeRef.betaReduce(Types.scala:2031)
	at scala.reflect.internal.Types$AliasTypeRef.betaReduce$(Types.scala:2031)
	at scala.reflect.internal.Types$AliasNoArgsTypeRef.betaReduce(Types.scala:2429)
 
        // The following four lines repeat continuously:  

	at scala.reflect.internal.Types$AliasTypeRef.normalizeImpl(Types.scala:2011)
	at scala.reflect.internal.Types$AliasTypeRef.normalizeImpl$(Types.scala:2010)
	at scala.reflect.internal.Types$AliasNoArgsTypeRef.normalizeImpl(Types.scala:2429)
	at scala.reflect.internal.Types$TypeRef.normalize(Types.scala:2250)

@SethTisue
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what's the top of the stack trace look like? maybe not the absolute top, but the part near the top that would show what phase of compilation it's happening during

@SethTisue SethTisue added this to the Backlog milestone Nov 27, 2018
@diesalbla
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diesalbla commented Nov 27, 2018 •
edited

That was the top of the stack trace, as I saw it on Scala 2.12.7. However, I have just tried this code on the 2.13 branch (the sbt scala command), and it seems that this, too, has already been fixed. This is the response it gets:

         implicitly[A <:< A#Type]
                            ^
<pastie>:8: error: malformed type: A#Type

@diesalbla diesalbla mentioned this issue Nov 27, 2018
Merged
@SethTisue SethTisue modified the milestones: Backlog, 2.13.0-RC1 Nov 27, 2018
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@SethTisue @gourlaysama @diesalbla @scabug