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singleton type pattern should use eq, not == for test #4577

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scabug opened this issue May 13, 2011 · 12 comments
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singleton type pattern should use eq, not == for test #4577

scabug opened this issue May 13, 2011 · 12 comments
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@adriaanm
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blocker has PR language spec patmat
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2.11.0-RC1

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@scabug
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scabug commented May 13, 2011

GI intend to conquer the pattern matcher this time. Have to do some ticketizing.

The following test case reveals multiple significant issues with equality, including calling equals when it's supposed to be using reference equality, and considering a stable identifier foo to be unreachable on the basis that _: foo.type had not matched. (It can actually learn nothing, because the one should be reference equality and the other should be a call to equals.)

object Test {
  val bippy    = new Symbol("bippy")
  val imposter = new Symbol("bippy")
  val notBippy = new Symbol("not-bippy")
  val syms = List(bippy, imposter, notBippy)

  class Symbol(val name: String) {
    override def equals(other: Any) = other match {
      case x: Symbol  => name == x.name
      case _          => false
    }
    override def toString = name
  }

  def f(s: Symbol) = s match {
    case _: bippy.type  => true
    case _              => false
  }
  def g(s: Symbol) = s match {
    case _: bippy.type => 1
    case `bippy`       => 2
    case _             => 3
  }
  
  def main(args: Array[String]): Unit = {
    // should be: true false false
    syms map f foreach println
    // should be: 1 2 3
    syms map g foreach println
  }
}
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scabug commented May 13, 2011

Imported From: https://issues.scala-lang.org/browse/SI-4577?orig=1
Reporter: @paulp

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scabug commented Feb 8, 2013

@paulp said:
Update Feb 2013: all bugs successfully made the transition from oldpatmat to newpatmat. Good job, bugs.

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scabug commented Apr 24, 2013

@paulp said:
Just for fun I'm marking this a blocker; it shouldn't be that hard to fix, and with the pattern matcher receiving so much love it seems wrong not to fix something so fundamental.

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scabug commented Apr 24, 2013

@paulp said:
Of course, with "blocker" the default priority in JIRA, I may have unwittingly consigned it to oblivion.

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scabug commented Apr 24, 2013

@paulp said:
In the interests of making the blockers a little blockier, I bulk-edited most of the "Blockers" down to "Major".

https://issues.scala-lang.org/secure/IssueNavigator.jspa?mode=hide&requestId=12202

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scabug commented Oct 15, 2013

@gkossakowski said:
Unassigning and rescheduling to M7 as previous deadline was missed.

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scabug commented Jan 14, 2014

@adriaanm said:
rock, meet hard place... I'm not sure we can fix this in 2.11

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scabug commented Jan 14, 2014

@paulp said:
I believe rock and hard place are already well acquainted.

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scabug commented Jan 29, 2014

@adriaanm said:
wip: https://github.com/adriaanm/scala/compare/t4577

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scabug commented Feb 19, 2014

@adriaanm said:
scala/scala#3558

@scabug scabug closed this as completed Feb 21, 2014
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scabug commented Mar 6, 2014

Stephen Compall (s11001001) said:
Yes. Thank you @adriaanm!

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scabug commented Mar 6, 2014

@adriaanm said:
Pleasure.

@scabug scabug added this to the 2.11.0-RC1 milestone Apr 7, 2017
@scabug scabug mentioned this issue Apr 7, 2017
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