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Can't define value class's value as implicit #9601

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scabug opened this issue Dec 21, 2015 · 2 comments
Open

Can't define value class's value as implicit #9601

scabug opened this issue Dec 21, 2015 · 2 comments
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valueclass
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@scabug
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scabug commented Dec 21, 2015

Seems you can't define a value class's value as implicit:

class IntW(implicit val n: Int) extends AnyVal
Foo.scala:1: error: value class may not be a member of another class
class Foo(implicit val n: Int) extends AnyVal
      ^
one error found

The use of Int here as an implicit class is just for reproduction purpose, it wouldn't be wise to do so.

The current workaround is to drop the implicit and define an implicit method:

class IntW(val n: Int) extends AnyVal {
  private implicit def implicitInt: Int = n 
}
@scabug
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scabug commented Dec 21, 2015

Imported From: https://issues.scala-lang.org/browse/SI-9601?orig=1
Reporter: @dwijnand
Affected Versions: 2.11.7

@scabug scabug added this to the Backlog milestone Apr 7, 2017
@hrhino
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hrhino commented Dec 7, 2017

The error is now

scala> class IntW(implicit val n: Int) extends AnyVal
<console>:11: error: value class needs to have exactly one val parameter
       class IntW(implicit val n: Int) extends AnyVal
             ^

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@scabug @hrhino