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regression in implicit divergence checking #7983

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scabug opened this issue Nov 19, 2013 · 2 comments
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regression in implicit divergence checking #7983

scabug opened this issue Nov 19, 2013 · 2 comments
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@scabug
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scabug commented Nov 19, 2013

package foo.bar.baz

class DivergenceTest {

  trait ColumnBase[T]

  trait ShapeLevel
  trait Flat extends ShapeLevel
  trait Lower extends Flat

  class Shape2[Level <: ShapeLevel, -M, U]

  implicit final def columnBaseShape[Level >: Flat <: ShapeLevel, T, C <: ColumnBase[_]]
                                    (implicit ev: C <:< ColumnBase[T]
                                    ): Shape2[Level, C, T] = ???

  implicit final def intShape[Level <: ShapeLevel, T]: Shape2[Level, Int, Int] = ???
  implicit final def tuple2Shape[Level <: ShapeLevel, M1,M2, U1,U2]
                                (implicit u1: Shape2[_ <: Level, M1, U1],
                                          u2: Shape2[_ <: Level, M2, U2]
                                ): Shape2[Level, (M1,M2), (U1,U2)] = ???

  def foo {
    class Coffees extends ColumnBase[Int]

    def map1[F, T](f: F)(implicit shape: Shape2[_ <: Flat, F, T]) = ???

    map1(((1, null: Coffees), 1))
    map1(((null: Coffees, 1), 1)) // fails
  }
}

Worked in 2.10.x, fails in 2.11 due to a change in dominates.

@scabug
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scabug commented Nov 19, 2013

Imported From: https://issues.scala-lang.org/browse/SI-7983?orig=1
Reporter: @retronym
Affected Versions: 2.11.0-M3

@scabug
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scabug commented Nov 19, 2013

@retronym said:
scala/scala#3160

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