support dependent argument types for constructor parameter lists (in the same way as for methods)

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scala> import scala.tools.nsc._
import scala.tools.nsc._

scala> def mkReifier(global: Global)(typer: global.analyzer.Typer) = typer
mkReifier: (global: scala.tools.nsc.Global)(typer: global.analyzer.Typer)global.analyzer.Typer

scala> class Reifier(global: Global)(typer: global.analyzer.Typer) { }
<console>:10: error: not found: value global
      class Reifier(global: Global)(typer: global.analyzer.Typer) { }
                                           ^

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Imported From: https://issues.scala-lang.org/browse/SI-5712?orig=1
Reporter: @paulp
Affected Versions: 2.10.0, 2.11.6
See #5700

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@retronym said:
Just happened across this looking into #5070, it struck me that it might need to be expanded for dependent constructor types.

override def isImmediatelyDependent = (sym ne NoSymbol) && (sym.owner.isMethod && sym.isValueParameter)

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@adriaanm said (edited on Jul 26, 2012 9:37:36 AM UTC):
I wonder why we're using an outer namer for parameter accessors.
Commenting out these lines fixes the test case.

    def namerOf(sym: Symbol): Namer = {
      val usePrimary = sym.isTerm && (
//           (sym.isParamAccessor)
//        ||
        (sym.isParameter && sym.owner.isPrimaryConstructor)
      )

      if (usePrimary) createPrimaryConstructorParameterNamer
      else innerNamer
    }

Here's a self-contained test case that also makes sure the constructor's type parameters stay in scope.

class Global {
  class Typer[T]
}

class Reifier[T](global: Global)(typer: global.Typer[T])

object Test {
  def mkReifier[T](global: Global)(typer: global.Typer[T]) = typer
}

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@adriaanm said (edited on Jul 26, 2012 10:20:19 AM UTC):
Lukas explains: we shouldn't see fields in the constructor signature, but we should see the parameter accessors.

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@gkossakowski said:
Unassigning and rescheduling to M7 as previous deadline was missed.

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Eduardo Pareja Tobes (eparejatobes) said:
just curious, why is this no longer considered a bug but an improvement?

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@adriaanm said:
Dependent method types were an improvement as well. This is an improvement to support dependent constructor types, which were never implemented. So, technically, they can't be buggy :-)

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Eduardo Pareja Tobes (eparejatobes) said:
OK thanks :)

something about the decreased priority and the unassigned state?

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@adriaanm said:
Exactly.

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Alexander Bulaev (alexbool) said:
Any news on this?

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Andrei Pozolotin (andrei.pozolotin) said:
Please implement?

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Nathan M (nemccarthy) said:
+1

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Owen Healy (ellbur) said:
This would be really useful. Scala's type system is amazing in that it makes dependent types usable by mere humans, but gaps like this partially undo that.

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@manojo said:
+1, any timeline on this?

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Ruben (lqbweb) said:
+1