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Bridge method omitted with type alias causes AbstractMethodError #8575

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scabug opened this issue May 10, 2014 · 5 comments
Closed

Bridge method omitted with type alias causes AbstractMethodError #8575

scabug opened this issue May 10, 2014 · 5 comments
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@retronym
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help wanted
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2.12.0-M1

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@scabug
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scabug commented May 10, 2014

This code throws an java.lang.AbstractMethodError:

  class E[F]
  class A
  class B
  class C

  trait Intf {
    type R
    type RR

    def f1(r: R) {
      val rr = f2(r)
      f3(rr) // This call throws an AbstractMethodError
    }

    def f2(r: R): RR
    def f3(r: RR)
  }

  class Impl extends Intf {
    type F = A with B
    type R = E[F]
    type RR = E[F with C]
    // works if I replace by:
    //type RR = E[A with B with C]

    override def f2(r: R): RR = new E[F with C]()
    override def f3(rr: RR) { println("This should be printed")}
  }

  new Impl().f1(new E[A with B]())
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scabug commented May 10, 2014

Imported From: https://issues.scala-lang.org/browse/SI-8575?orig=1
Reporter: Mikael Valot (mikaelv)
Affected Versions: 2.10.4, 2.11.0

@scabug
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scabug commented Sep 13, 2014 •
edited by retronym

Jonathan Brachthäuser (b-studios) said:
Added a byte code comparison the with working version (where the type alias is manually dealiased to E[A with B with C]) to https://gist.github.com/b-studios/e06f741434b2119ed0f2

The main difference is that the following method implementation is generated for the working version, while it isn't for the version with E[F with C]:

public java.lang.Object id(java.lang.Object);
  Code:
     0: aload_0       
     1: aload_1       
     2: checkcast     #27                 // class E
     5: invokevirtual #29                 // Method id:(LE;)LE;
     8: areturn

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scabug commented Sep 14, 2014

@Blaisorblade said:
I and Jona took a look today: he minimized the bug report and wrote a minimal fix — PR coming soon.

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scabug commented Sep 14, 2014

Jonathan Brachthäuser (b-studios) said:
scala/scala#3979

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scabug commented Nov 7, 2014

@retronym said:
scala/scala#3981

@scabug scabug closed this as completed Nov 7, 2014
@scabug scabug added this to the 2.12.0-M1 milestone Apr 7, 2017
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