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Auxiliary constructors in Value Classes lead to runtime errors. #6148

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scabug opened this issue Jul 27, 2012 · 3 comments

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scabug commented Jul 27, 2012

scala> class A(val x: Int) extends AnyVal { def this(s: String) = this(s.length) }
defined class A

scala> new A("a") == new A("b")
java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
    at scala.runtime.BoxesRunTime.unboxToInt(Unknown Source)
    at .<init>(<console>:9)
    at .<clinit>(<console>)

scala> class X(val a: Int) extends AnyVal { def this(x: String) = this(0) }
defined class X

scala> new X("").a
java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
    at

Troublesome spots in the implementation:

https://github.com/scala/scala/blob/39fc4aa84/src/compiler/scala/tools/nsc/transform/Erasure.scala#L362

https://github.com/scala/scala/blob/39fc4aa84/src/compiler/scala/tools/nsc/transform/Erasure.scala#L1003

https://github.com/scala/scala/blob/39fc4aa84/src/compiler/scala/tools/nsc/transform/PostErasure.scala#L36

https://github.com/scala/scala/blob/39fc4aa84/src/compiler/scala/tools/nsc/transform/PostErasure.scala#L46

I tried to constrain these spots to only consider primary constructor, but this triggered a compiler crash which I'm yet to pin down.

A heavy handed approach would be to disallow secondary constructors for now.

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scabug commented Jul 27, 2012

Imported From: https://issues.scala-lang.org/browse/SI-6148?orig=1
Reporter: @retronym
See #5799, #6090

Author

scabug commented Jul 29, 2012

@retronym said:
scala/scala#1011

Author

scabug commented Aug 1, 2012

@soc said:
Fixed in aad84ecba3.

scabug closed this as completed

scabug added this to the 2.10.0-M6 milestone

scabug assigned odersky

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