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ClassFormatError in specialized classes with override val mixins #9965

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scabug opened this issue Oct 15, 2016 · 2 comments
Open

ClassFormatError in specialized classes with override val mixins #9965

scabug opened this issue Oct 15, 2016 · 2 comments
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specialization
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Backlog

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@scabug
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scabug commented Oct 15, 2016

Not sure if this construct should be supported or not, but in the latter case I guess the compiler should complain instead.

object Playground extends App {
	trait I[@specialized T] {
		def fun :T=>T
		def m(value :T) :T
	}

	trait M[@specialized T] extends I[T]{
		override def fun = m _
	}

	trait V[@specialized T] extends I[T] {
		abstract override val fun = super.fun
	}

	class B[@specialized T] extends I[T] with M[T] with V[T] {
		override def m(value :T) = value
	}

	val subject = new B[Int]
	println(subject.fun(42))
}

Produces

Exception in thread "main" java.lang.ClassFormatError: Duplicate method name&signature in class file Playground$B$mcI$sp
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:467)
	at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at Playground.main(Playground.scala)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
@scabug
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scabug commented Oct 15, 2016

Imported From: https://issues.scala-lang.org/browse/SI-9965?orig=1
Reporter: Marcin Mościcki (mmoscicki)
Affected Versions: 2.11.8

@scabug
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scabug commented Oct 15, 2016

Marcin Mościcki (mmoscicki) said:
Oh, it seems it's slightly more serious, as simple override val instead of abstract override val is enough:

trait V[@specialized T] extends I[T] {
    override val fun = m _
}

And simplified whole snippet:

trait I[@specialized T] {
	def fun :T=>T
	def m(value :T) :T
}

trait M[@specialized T] extends I[T]{
	override def fun = m _
}

trait V[@specialized T] extends I[T] {
	override val fun = m _
}

class B[@specialized T] extends I[T] with M[T] with V[T] {
	override def m(value :T) = value
}

class C extends B[Int] {
	override def m(value: Int): Int = value
}

val subject = new B[Int]
println(subject.fun(42))

@scabug scabug added the quickfix label Apr 7, 2017
@SethTisue SethTisue added this to the Backlog milestone Jan 14, 2024
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