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Macros are not compatible with structural types #7340

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scabug opened this issue Apr 7, 2013 · 5 comments
Open

Macros are not compatible with structural types #7340

scabug opened this issue Apr 7, 2013 · 5 comments
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@scabug
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@scabug scabug commented Apr 7, 2013

This code will type-check but it will fail in runtime, as Macros dont generate runtime bytecode.

// A.scala
import scala.reflect.macros.Context
object A {
  def hello_impl(c:Context)() :c.Expr[Unit] = {
    import c.universe._
    reify {
      println("hello world")
    }
  }
}
// B.scala
import scala.language.experimental.macros
class B{
def hello():Unit = macro A.hello_impl
}
// C.scala
object C extends App{
  type greeter = {
    def hello():Unit;
  }
  val g:greeter= new B
  g.hello()
}

running such app raises java.lang.NoSuchMethodException: B.hello()

It also interferes a lot with how some java libraries work: for example Amazon DynamoDB SDK uses reflection to get all getters and setters, if some of them are defined by macros, they will be unreachable in runtime using reflection.

@scabug
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@scabug scabug commented Apr 7, 2013

Imported From: https://issues.scala-lang.org/browse/SI-7340?orig=1
Reporter: @DarkDimius
Affected Versions: 2.10.1

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@scabug
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@scabug scabug commented Jul 10, 2013

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@scabug
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@scabug scabug commented Aug 31, 2013

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@SethTisue
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@SethTisue SethTisue commented Mar 3, 2018

closing for presumed staleness. comment/reopen if you can verify this is still relevant to current Scala

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@SethTisue SethTisue closed this Mar 3, 2018
@SethTisue SethTisue removed the has PR label Mar 3, 2018
@lrytz lrytz reopened this Mar 3, 2018
@lrytz
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@lrytz lrytz commented Mar 3, 2018

still on

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