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Cannot create an instance of the case class with some encoded field names #10825

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plokhotnyuk opened this issue Apr 12, 2018 · 10 comments
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Cannot create an instance of the case class with some encoded field names #10825

plokhotnyuk opened this issue Apr 12, 2018 · 10 comments
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name mangling runtime crash should compile

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@plokhotnyuk
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plokhotnyuk commented Apr 12, 2018 •
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It looks like a bug in scalac and affects case classes which have 2 fields where name of one is a prefix for the another name that contains a character that should be encoded immediately after the prefix (like o and o-o).

For 2.11.12 I got a compilation error:

[error] scala.reflect.internal.Types$TypeError: type mismatch;
[error]  found   : Int
[error]  required: Seq
[error] 	at scala.tools.nsc.typechecker.Contexts$ThrowingReporter.handleError(Contexts.scala:1402)
[error] 	at scala.tools.nsc.typechecker.Contexts$ContextReporter.issue(Contexts.scala:1254)
[error] 	at scala.tools.nsc.typechecker.Contexts$Context.issue(Contexts.scala:573)
[error] 	at scala.tools.nsc.typechecker.ContextErrors$ErrorUtils$.issueTypeError(ContextErrors.scala:106)

While in 2.12 it fails in the runtime during a call of the constructor:

java.lang.Integer cannot be cast to scala.collection.Seq
java.lang.ClassCastException: java.lang.Integer cannot be cast to scala.collection.Seq
	at Publication.<init>(KebabFieldNameSpec.scala:3)
	at KebabFieldNameSpec.$anonfun$new$2(KebabFieldNameSpec.scala:8)
	at org.scalatest.OutcomeOf.outcomeOf(OutcomeOf.scala:85)
	at org.scalatest.OutcomeOf.outcomeOf$(OutcomeOf.scala:83)
	at org.scalatest.OutcomeOf$.outcomeOf(OutcomeOf.scala:104)
	at org.scalatest.Transformer.apply(Transformer.scala:22)

Code to reproduce:

import org.scalatest.{Matchers, WordSpec}

case class Publication(title: String, author: String, `reference-count`: Int, reference: Seq[String])

class KebabFieldNameSpec extends WordSpec with Matchers {
  "Publication" should {
    "be created by the constructor" in {
      new Publication("", "", 0, Nil)
    }
  }
}
@plokhotnyuk plokhotnyuk mentioned this issue Apr 12, 2018
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@plokhotnyuk plokhotnyuk changed the title Cannot create instance of the case class with some encoded field names Cannot create an instance of the case class with some encoded field names Apr 12, 2018
@plokhotnyuk
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plokhotnyuk commented Apr 12, 2018 •
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W/a for this scalac bug is to move a definition of the field with encoded chars (`reference-count` in our case) to be after the field that is affected by the exception (after the reference field):

case class Publication(title: String, author: String, reference: Seq[String], `reference-count`: Int)

@hrhino
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hrhino commented Apr 12, 2018 •
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    // The constructor parameter with given name. This means the parameter
    // has given name, or starts with given name, and continues with a `$` afterwards.
    def parameterNamed(name: Name): Symbol = {
      def matchesName(param: Symbol) = param.name == name || param.name.startsWith(name + nme.NAME_JOIN_STRING) // nme.NAME_JOIN_STRING = "$"

      primaryConstrParams filter matchesName match {
        case Nil    => abort(name + " not in " + primaryConstrParams)
        case p :: _ => p
      }

More fallout from using $ for everything name-y. (#2806) This may hail from '06: scala/scala@cb7711d.

@som-snytt
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Probably the same problem as #10625 where Constructors looks at prefixes.

@som-snytt
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Another symptom #8831

@SethTisue SethTisue added this to the Backlog milestone Jun 7, 2018
@plokhotnyuk plokhotnyuk mentioned this issue Oct 18, 2018
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@som-snytt
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@hrhino should this and 10625 also be closed in favor of 8831 as an umbrella issue? Asking in case you understand any nuances. I haven't re-read the issues.

@hrhino
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hrhino commented Oct 18, 2018

I'm not a very nuanced person. Re-rereading the issues, this is almost certainly a duplicate of #8831, and has the same root cause as #10625 (IIRC, if I remember constructors) but I don't feel confident saying, externally, that it's a duplicate. Not sure what the criteria for that are.

@hrhino
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hrhino commented Oct 18, 2018

Also, what happened to the touted GitHub "duplicate of" feature from a few months ago? Did it get rebased away?

@som-snytt
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I'll take a @hrhino "almost certainly" and "don't feel confident" any day. I think the issue that says "bizarre" always takes priority.

On github, it's easy to navigate between linked issues, so I won't try to copy/paste to #8831.

@dwijnand
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Duplicate of #8831

@dwijnand dwijnand marked this as a duplicate of #8831 May 13, 2019
@SethTisue SethTisue removed this from the Backlog milestone May 13, 2019
@hrhino
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hrhino commented Oct 26, 2019

Woah, I just noticed that when @dwijnand says "duplicate of #...", github listens!

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@SethTisue @dwijnand @som-snytt @plokhotnyuk @hrhino