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SAM type does not support dependent type #9897

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scabug opened this issue Aug 20, 2016 · 4 comments
Open

SAM type does not support dependent type #9897

scabug opened this issue Aug 20, 2016 · 4 comments
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dependent types enhancement fixed in Scala 3 This issue does not exist in the Scala 3 compiler (https://github.com/lampepfl/dotty/) infer typelevel typer
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@scabug
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scabug commented Aug 20, 2016 

$ scala -Xexperimental
Welcome to Scala 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_77).
Type in expressions for evaluation. Or try :help.

scala>     trait Container {
     |       type Child
     | 
     |       def child: Child
     |     }
defined trait Container

scala>     trait Sam {
     |       def apply(container: Container): container.Child
     |     }
defined trait Sam

scala>     val sam: Sam = { container: Container => container.child }
<console>:13: error: type mismatch;
 found   : container.Child
 required: container.Child
           val sam: Sam = { container: Container => container.child }
                                                 ^
@scabug
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scabug commented Aug 20, 2016

Imported From: https://issues.scala-lang.org/browse/SI-9897?orig=1
Reporter: @Atry
Affected Versions: 2.11.8, 2.12.0-RC1

@scabug
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scabug commented Sep 29, 2016

@SethTisue said:
Is it reproducible in 2.12 as well? (The -Xexperimental stuff in 2.11 is now unmaintained.)

@scabug
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scabug commented Sep 30, 2016

@Atry said:

Welcome to Scala 2.12.0-RC1 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_77).
Type in expressions for evaluation. Or try :help.

scala> trait Container {
     |   type Child
     |   def child: Child
     | }
defined trait Container

scala> trait Sam {
     |   def apply(container: Container): container.Child
     | }
defined trait Sam

scala> val sam: Sam = { container: Container => container.child }
<console>:13: error: type mismatch;
 found   : Container => Container#Child
 required: Sam
       val sam: Sam = { container: Container => container.child }
                                             ^

scala> val r: Runnable = { () => }
r: Runnable = $$Lambda$1193/369956118@2c418b3a

TiarkRompf referenced this issue in b-studios/scala-effekt May 25, 2017
@b-studios
Add a simple testfile
96237f8
@Atry Atry mentioned this issue Nov 28, 2017
Closed
@SethTisue SethTisue added this to the Backlog milestone Nov 2, 2023
@SethTisue SethTisue added the fixed in Scala 3 This issue does not exist in the Scala 3 compiler (https://github.com/lampepfl/dotty/) label Nov 2, 2023
@SethTisue
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SethTisue commented Nov 2, 2023 •
edited

in more conveniently pastable form,

trait Container {
  type Child
  def child: Child
}
trait Sam {
  def apply(container: Container): container.Child
}
val sam: Sam = { (container: Container) => container.child }

error on 2.12.18:

error: type mismatch;
 found   : Container => Container#Child
 required: Sam

error on 2.13.12:

error: type mismatch;
                found   : container.Child
                required: container.Child

it compiles on Scala 3.3.1

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