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Trivial inline identity function causes runtime NoClassDefFound error in resulting code #23279

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#23432
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Trivial inline identity function causes runtime NoClassDefFound error in resulting code#23279
#23432
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area:inlineitype:bug
@neko-kai

Description

@neko-kai
neko-kai
opened on May 28, 2025 · edited by neko-kai
Contributor

Compiler version

3.3.6, 3.7.0 and 3.7.1-RC2

Minimized code

inline def simpleInlineWrap(f: => Any): Unit = f

@main def main(): Unit = {
  simpleInlineWrap {
    object lifecycle {
      object Lifecycle {
        trait FromZIO
      }
    }
    object defn {
      val Lifecycle: lifecycle.Lifecycle.type = lifecycle.Lifecycle
    }
    val xa: defn.Lifecycle.type = defn.Lifecycle
  }
}

https://scastie.scala-lang.org/fcE9r7cwQBSw7m5XwrrR1w - Scastie running on 3.7.1-RC2

Output

java.lang.NoClassDefFoundError: main$package$_$lifecycle$Lifecycle$
	at main$package$.f$proxy1$1(main.scala:13)
	at main$package$.main(main.scala:4)
	at main.main(main.scala:3)

Expectation

Expected not to throw NoClassDefFound error. Removing inline from simpleInlineWrap causes the code to work as expected.

NB: encountered when using ScalaTest, which at some point started wrapping all user tests via inline functions

Activity

neko-kai
added
itype:bug
stat:needs triageEvery issue needs to have an "area" and "itype" label
on May 28, 2025
neko-kai
added a commit that references this issue on May 28, 2025

Fix Scala 3 build by working around a newly found scala/scala3#23279

52e4d47
som-snytt

som-snytt commented on May 28, 2025

@som-snytt
som-snytt
on May 28, 2025
Contributor

The working case at flatten has

        val xa:
          i23279$package$lifecycle$2.this.i23279$package$lifecycle$2$Lifecycle
           = this.defn$1(defn$lzy1, lifecycle$lzy1).Lifecycle()

before flatten

        val xa: lifecycle$2.this.Lifecycle =
          this.defn$1(defn$lzy1, lifecycle$lzy1).Lifecycle()

The broken proxy has

        val xa: i23279$package.lifecycle.i23279$package$_$lifecycle$Lifecycle =
          this.defn$1(defn$lzy1, lifecycle$lzy1).Lifecycle().asInstanceOf[
            i23279$package.lifecycle.i23279$package$_$lifecycle$Lifecycle]

before flatten

        val xa: i23279$package.lifecycle.Lifecycle =
          this.defn$1(defn$lzy1, lifecycle$lzy1).Lifecycle().asInstanceOf[
            i23279$package.lifecycle.Lifecycle]

where it should be lifecycle$2 after lambdalift.

neko-kai
added a commit that references this issue on May 29, 2025

Fix regression in 3.0.0: properly dealias nested singletons on Scala 2 (

98ba301
Gedochao
added
area:inline
and removed
stat:needs triageEvery issue needs to have an "area" and "itype" label
on May 29, 2025
som-snytt
self-assigned this
on Jun 1, 2025
jchyb
mentioned this on Jun 26, 2025
jchyb

jchyb commented on Jun 26, 2025

@jchyb
jchyb
on Jun 26, 2025
Contributor

@som-snytt Apologies for threading on your ground, but the issue seems pretty severe and I think I managed to find the fix (#23432). Thank you for the initial investigation here

som-snytt
removed their assignment
on Jun 26, 2025
odersky
closed this as completedin #23432on Jun 27, 2025
smarter
added a commit that references this issue on Jun 27, 2025

Fix Symbol.info remapping in TreeTypeMap (scala#23432)

d995b33
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        Trivial inline identity function causes runtime `NoClassDefFound` error in resulting code · Issue #23279 · scala/scala3