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Covariance Check #8225

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scabug opened this issue Feb 1, 2014 · 3 comments
Closed

Covariance Check #8225

scabug opened this issue Feb 1, 2014 · 3 comments
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@adriaanm
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blocker regression typer

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@scabug
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scabug commented Feb 1, 2014

This no more compiles but fails with "Covariant type occurs in invariant position":

import language.higherKinds

trait ELI[N]
trait Companion[+CC[N, E[X] <: ELI[X]]] {
  protected type Coll = CC[_,Nothing]
}

Adding @uncheckedVariance doesn't help either.
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scabug commented Feb 1, 2014

Imported From: https://issues.scala-lang.org/browse/SI-8225?orig=1
Reporter: Sonnenschein (sonnenschein)
Affected Versions: 2.11.0-M8
See #6566

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scabug commented Feb 1, 2014

@retronym said:
You have to make it protected[this], after the fix for #6566.

import language.higherKinds
 
trait ELI[N]
trait Companion[+CC[N, E[X] <: ELI[X]]] {
  protected[this] type Coll = CC[_,Nothing]
}

@scabug scabug closed this as completed Feb 1, 2014
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scabug commented Mar 21, 2014

@adriaanm said:
See also #7093 on an important note regarding protected[this].

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