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isModule in macro/reflection API always returns false #6012

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scabug opened this issue Jul 1, 2012 · 3 comments
Closed

isModule in macro/reflection API always returns false #6012

scabug opened this issue Jul 1, 2012 · 3 comments
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@xeno-by
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blocker macros reflection
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2.10.0

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@scabug
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scabug commented Jul 1, 2012

isModule always seems to return false:

scala> import reflect.runtime.universe._
import reflect.runtime.universe._

scala> object Foo
defined module Foo

scala> typeOf[Foo.type]
res0: reflect.runtime.universe.Type = Foo.type

scala> res0.typeSymbol.isModule
res1: Boolean = false

scala> res0.widen.typeSymbol.isModule
res2: Boolean = false

scala> res0.underlying.typeSymbol.isModule
res3: Boolean = false

scala> res0.erasure.typeSymbol.isModule
res4: Boolean = false

It only seems to be possible to get it to return true by reaching into the innards of the compiler:

scala> res1.getClass
res3: Class[_ <: reflect.runtime.universe.Symbol] = class scala.reflect.internal.Symbols$ModuleClassSymbol

scala> res1.isModuleClass
<console>:14: error: value isModuleClass is not a member of reflect.runtime.universe.Symbol
              res1.isModuleClass
                   ^

scala> res1.asInstanceOf[scala.tools.nsc.Global#Symbol].isModuleClass
res5: Boolean = true
@scabug
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scabug commented Jul 1, 2012

Imported From: https://issues.scala-lang.org/browse/SI-6012?orig=1
Reporter: @paulbutcher
Affected Versions: 2.10.0-M4

@scabug
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scabug commented Jul 1, 2012

@paulbutcher said:
Update - companionSymbol does return something that returns true:

scala> object Foo
defined module Foo

scala> typeOf[Foo.type]
res0: reflect.runtime.universe.Type = Foo.type

scala> res0.typeSymbol.companionSymbol.isModule
res1: Boolean = true

Unfortunately, this doesn't help much, because the same is also true if we have:

scala> :paste
// Entering paste mode (ctrl-D to finish)

class Foo

object Foo

// Exiting paste mode, now interpreting.

defined class Foo
defined module Foo

scala> typeOf[Foo]
res1: reflect.runtime.universe.Type = Foo

scala> res1.typeSymbol.isModule
res2: Boolean = false

scala> res1.typeSymbol.companionSymbol.isModule
res3: Boolean = true

So this isn't a useful way to tell the difference between a class and its companion object :-(

@scabug
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scabug commented Jul 3, 2012

@xeno-by said:
Fixed by scala/scala@f5b0d7b

@scabug scabug closed this as completed Jul 3, 2012
@scabug scabug added this to the 2.10.0 milestone Apr 7, 2017
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