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abstract override crasher. #4134

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scabug opened this issue Jan 6, 2011 · 5 comments
Closed

abstract override crasher. #4134

scabug opened this issue Jan 6, 2011 · 5 comments
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@scabug scabug commented Jan 6, 2011

trait T1 {
  def f: Unit
}                                                                               

trait T2 extends T1 {
  abstract override def f: Unit = "in T1"
  def something = super.f  // So the "abstract override" is needed
}                                                                               

trait Q1 {
  def f: Unit = "bippy"
}                                                                               

trait T3 extends T2 with Q1 {
  abstract override def f: Unit = "in T2"
}

object Test {
  def main(args: Array[String]): Unit = {
    new T3 { }
  }
}
% scalac29 -version
Scala compiler version 2.9.0.r23890-b20110103193501 -- Copyright 2002-2010, LAMP/EPFL
% scalac29 0106.scala 
Exception in thread "main" java.lang.AssertionError: assertion failed: method f
	at scala.Predef$$.assert(Predef.scala:99)
	at scala.tools.nsc.transform.Mixin$$$$anonfun$$scala$$tools$$nsc$$transform$$Mixin$$$$rebindSuper$$1.apply(Mixin.scala:110)
	at scala.tools.nsc.transform.Mixin$$$$anonfun$$scala$$tools$$nsc$$transform$$Mixin$$$$rebindSuper$$1.apply(Mixin.scala:95)
	at scala.tools.nsc.symtab.SymbolTable.atPhase(SymbolTable.scala:96)
	at scala.tools.nsc.transform.Mixin.scala$$tools$$nsc$$transform$$Mixin$$$$rebindSuper(Mixin.scala:95)
	at scala.tools.nsc.transform.Mixin$$$$anonfun$$mixinTraitMembers$$1$$1.apply(Mixin.scala:325)
	at scala.tools.nsc.transform.Mixin$$$$anonfun$$mixinTraitMembers$$1$$1.apply(Mixin.scala:278)
	at scala.collection.LinearSeqOptimized$$class.foreach(LinearSeqOptimized.scala:61)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.tools.nsc.transform.Mixin.mixinTraitMembers$$1(Mixin.scala:278)
	at scala.tools.nsc.transform.Mixin$$$$anonfun$$addMixedinMembers$$3.apply(Mixin.scala

Not that the version is super relevant. Even the line numbers are stable.

% scalac26 -version
Scala compiler version 2.6.1-final -- (c) 2002-2007 LAMP/EPFL
% scalac26 0106.scala 
Exception in thread "main" java.lang.AssertionError: assertion failed: method f
	at scala.Predef$$.assert(Predef.scala:96)
	at scala.tools.nsc.transform.Mixin$$$$anonfun$$scala$$tools$$nsc$$transform$$Mixin$$$$rebindSuper$$1.apply(Mixin.scala:111)
	at scala.tools.nsc.transform.Mixin$$$$anonfun$$scala$$tools$$nsc$$transform$$Mixin$$$$rebindSuper$$1.apply(Mixin.scala:96)
	at scala.tools.nsc.symtab.SymbolTable.atPhase(SymbolTable.scala:89)
	at scala.tools.nsc.transform.Mixin.scala$$tools$$nsc$$transform$$Mixin$$$$rebindSuper(Mixin.scala:96)
	at scala.tools.nsc.transform.Mixin$$$$anonfun$$mixinTraitMembers$$1$$1.apply(Mixin.scala:257)
	at scala.tools.nsc.transform.Mixin$$$$anonfun$$mixinTraitMembers$$1$$1.apply(Mixin.scala:224)
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@scabug scabug commented Jan 6, 2011

Imported From: https://issues.scala-lang.org/browse/SI-4134?orig=1
Reporter: @paulp
Other Milestones: 2.10.0-M3

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@scabug scabug commented Apr 6, 2012

@som-snytt said:
I took a look and submitted pull request 359.

This commit just changes the assert on a bad abstract super.m to a compiler error. Probably it's the not that simple, right? In this case, review (and rejection) is easy; but if it weren't, should I ask on scala-internals or on the jira ticket? By way of not wasting people's time? I was just looking for small bugs as an excuse to look at code.

This is a great learning experience, but in mid-learning-curve, I don't have a lot of visibility into the code or even a feeling that I'm not doing something dumb or, worse, counter-productive.

Needless to add, test suite passes and collaborator license agreement is verified.

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@scabug scabug commented Apr 6, 2012

@paulp said:
scala-internals is the best because a lot of people might respond there, and here you have a potential audience of about five. The patch looks like an improvement, except we don't use Option[Symbol]; that's what NoSymbol is for. It's in develop along with a patch from me addressing that.

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@scabug scabug commented Apr 6, 2012

@som-snytt said:
OK, thanks. I'm glad I resisted the urge to use Option.fold for the first time.

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@scabug scabug commented Apr 28, 2012

@som-snytt said:
scala/scala#359
72f6f0e57ca490b36cef62a3be2a8b3261476cd2

@scabug scabug closed this Apr 28, 2012
@scabug scabug added the help wanted label Apr 7, 2017
@scabug scabug added this to the 2.10.0-M2 milestone Apr 7, 2017
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