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implicit generic value class causes compilation error #8018

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scabug opened this issue Nov 29, 2013 · 2 comments
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implicit generic value class causes compilation error #8018

scabug opened this issue Nov 29, 2013 · 2 comments
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@retronym
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2.11.0-M8

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@scabug
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scabug commented Nov 29, 2013

This code does not compile:

object Test {

  sealed trait Parser[I]

  implicit class ParserOps[I](val parser: Parser[I]) extends AnyVal {

    def trans(pf: PartialFunction[Parser[I], Parser[I]]): Parser[I] = {
      parser
    }

    def withErrorValue(errorValue: => Parser[I]): Parser[I] = parser trans {
      case p => p
    }

  }

}

The error is:

overriding method applyOrElse in trait PartialFunction of type [A1 <: eu.swdev.parser.push.Test.Parser[I], B1 >: eu.swdev.parser.push.Test.Parser[I]](x: A1, default: A1 => B1)B1;
 method applyOrElse has incompatible type
    def withErrorValue(errorValue: => Parser[I]): Parser[I] = parser trans {
object creation impossible, since method isDefinedAt in trait PartialFunction of type (x: eu.swdev.parser.push.Test.Parser[I])Boolean is not defined
(Note that A does not match eu.swdev.parser.push.Test.Parser[I])
    def withErrorValue(errorValue: => Parser[I]): Parser[I] = parser trans {
                                                                           ^                                                                           ^

The compilation error disappears if

  • the ParserOps class is changed such that it does not extend
    AnyVal or
  • the type parameter I is removed from the Parser class
@scabug
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scabug commented Nov 29, 2013

Imported From: https://issues.scala-lang.org/browse/SI-8018?orig=1
Reporter: stefan.wachter-at-gmx.de
Duplicates #8011

@scabug scabug closed this as completed Nov 29, 2013
@scabug
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scabug commented Nov 29, 2013

@retronym said:
Duplicate of #8011, fixed in 2.11.0-M8.

Fixed in scala/scala@cb37548

scalac-hash cb37548ef85d471951867b9f8a97cb9b9820fc66 sandbox/test.scala
(remotes/origin/2.10.2) ~/code/scala2 scalac-hash cb37548ef85d471951867b9f8a97cb9b9820fc66~1 sandbox/test.scala
sandbox/test.scala:11: error: overriding method applyOrElse in trait PartialFunction of type [A1 <: Test.Parser[I], B1 >: Test.Parser[I]](x: A1, default: A1 => B1)B1;
 method applyOrElse has incompatible type
    def withErrorValue(errorValue: => Parser[I]): Parser[I] = parser trans {
                                                                           ^
one error found

@scabug scabug added this to the 2.11.0-M8 milestone Apr 7, 2017
This was referenced Apr 7, 2017
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