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incorrect rewriting of value class == in presence of overloading. #6090

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scabug opened this issue Jul 16, 2012 · 3 comments
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incorrect rewriting of value class == in presence of overloading. #6090

scabug opened this issue Jul 16, 2012 · 3 comments
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@odersky
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valueclass
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2.10.0-M5

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@scabug
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scabug commented Jul 16, 2012 •
edited by retronym

Inspired by #6072:

scala> new V(new X) == new V(new X)
res2: Boolean = false

scala> class X { def ==(other: X) = ??? }
defined class X

scala> class V(val x: X) extends AnyVal
defined class V

scala> new V(new X) == new V(new X)
scala.NotImplementedError: an implementation is missing
	at scala.Predef$.$qmark$qmark$qmark(Predef.scala:243)
	at X.$eq$eq(<console>:8)
	at .<init>(<console>:10)

I'd expect this to dispatch to Any#==.
@scabug
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scabug commented Jul 16, 2012

Imported From: https://issues.scala-lang.org/browse/SI-6090?orig=1
Reporter: @retronym
Affected Versions: 2.10.0
See #6072

@scabug
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scabug commented Jul 16, 2012

@retronym said:
The potential complementary bug doesn't exist:

scala> class X(val a: Int) extends AnyVal { def ==(other: X) = true }
defined class X

scala> new X(0) == new X(1)
res7: Boolean = true

The tree scrutinized by PostErasureTransformer here is:

  X.this.extension$==(new X(0.$asInstanceOf[Int]()).a().$asInstanceOf[Int](), new X(1.$asInstanceOf[Int]()).a().$asInstanceOf[Int]())

But in any case the match should be modified to replace cmp == nme.EQ || cmp == nme.NE with a symbol based check against Object_== / Object_!=.

@scabug
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scabug commented Jul 21, 2012

@odersky said:
In fact, the behavior is consistent with case classes. Both forward to a method named ==, not necessarily Any_==. I sharpened the test in posterasure according to the suggestion.

@scabug scabug closed this as completed Jul 28, 2012
@scabug scabug added this to the 2.10.0-M5 milestone Apr 7, 2017
This was referenced Apr 7, 2017
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