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tag generation fails weirdly for higher-kinded types #7686

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scabug opened this issue Jul 22, 2013 · 2 comments
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tag generation fails weirdly for higher-kinded types #7686

scabug opened this issue Jul 22, 2013 · 2 comments
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@scabug
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@scabug scabug commented Jul 22, 2013

import scala.reflect.runtime.universe._

object Test extends App {
  def test[B[_]](implicit tt: TypeTag[B[_]]) = ???
  test[Option]
}
17:26 ~/Projects/210x/sandbox (2.10.x)$ s -Yreify-debug
reifying = Option[_]
universe = scala.reflect.runtime.`package`.universe
mirror = <empty>
ExistentialType(List(newTypeName("_$1")), TypeRef(ThisType(scala), scala.Option, List(TypeRef(NoPrefix, newTypeName("_$1"), List()))))
tough type: Option[_] (ExistentialType)
Sym def: type _$1 (type)
Sym def: value tt (value)
Locatable: method test (method) owned by object Test (module class) at Test
TypeRef(ThisType(scala), scala.Option, List(TypeRef(NoPrefix, newTypeName("_$1"), List())))
ThisType(scala)
TypeRef(NoPrefix, newTypeName("_$1"), List())
NoPrefix
Filling in: value tt (value)
TypeRef(SingleType(SingleType(SingleType(SingleType(SingleType(ThisType(<root>), scala), scala.reflect), scala.reflect.runtime), scala.reflect.runtime.package), newTermName("universe")), newTypeName("TypeTag"), List(ExistentialType(List(newTypeName("_$1")), TypeRef(NoPrefix, newTypeName("B"), List(TypeRef(NoPrefix, newTypeName("_$1"), List()))))))
SingleType(SingleType(SingleType(SingleType(SingleType(ThisType(<root>), scala), scala.reflect), scala.reflect.runtime), scala.reflect.runtime.package), newTermName("universe"))
SingleType(SingleType(SingleType(SingleType(ThisType(<root>), scala), scala.reflect), scala.reflect.runtime), scala.reflect.runtime.package)
SingleType(SingleType(SingleType(ThisType(<root>), scala), scala.reflect), scala.reflect.runtime)
SingleType(SingleType(ThisType(<root>), scala), scala.reflect)
SingleType(ThisType(<root>), scala)
ThisType(<root>)
Locatable: value universe (getter) owned by package package (package object class) at scala.reflect.runtime.package
Locatable: trait TypeTag (trait) owned by trait TypeTags (trait) at scala.reflect.api.TypeTags
ExistentialType(List(newTypeName("_$1")), TypeRef(NoPrefix, newTypeName("B"), List(TypeRef(NoPrefix, newTypeName("_$1"), List()))))
tough type: B[_] (ExistentialType)
TypeRef(NoPrefix, newTypeName("B"), List(TypeRef(NoPrefix, newTypeName("_$1"), List())))
splicing B[_$1]
launching implicit search for scala.reflect.runtime.`package`.universe.TypeTag[B[_$1]]
implicit search was fruitless
trying to splice as manifest
no manifest in scope
Test.scala:7: error: No TypeTag available for Option[_]
  test[Option]
      ^
one error found
@scabug
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@scabug scabug commented Jul 22, 2013

@scabug scabug added this to the Backlog milestone Apr 7, 2017
hrhino added a commit to hrhino/scala that referenced this issue Jan 1, 2020
I nearly resolved to clear the scala/bug backlog this year.

Fixes scala/bug#3899
Fixes scala/bug#7686
Fixes scala/bug#9668
hrhino added a commit to hrhino/scala that referenced this issue Jan 7, 2020
I nearly resolved to clear the scala/bug backlog this year.

Fixes scala/bug#3899
Fixes scala/bug#7686

The test case for scala/bug#3899 was contributed oh so many years ago by retronym, so this is

Co-Authored-By: "Jason Zaugg" <jzaugg@gmail.com>
@lrytz
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@lrytz lrytz commented Jan 9, 2020

@lrytz lrytz closed this Jan 9, 2020
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