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  1. Minecraft: Java Edition
  2. MC-137746

Crash when generating at exactly the top of the world


    • Icon: Bug Bug
    • Resolution: Fixed
    • Minecraft 18w47b
    • Minecraft 1.13.2, Minecraft 18w43a, Minecraft 18w43b, Minecraft 18w44a, Minecraft 18w45a, Minecraft 18w46a
    • None
    • Unconfirmed
    • (Unassigned)

      The bug

      When creating a superflat world with the top block level at exactly y=256 the game crashes during generation or almost immediately after entering the world. The preset 255*minecraft:air,minecraft:stone;minecraft:plains;village is one preset that does this.

      Disabling surface structures like villages seems to avoid the problem. Enabling normal decoration like trees and grass also works fine.

      I haven't yet tested whether or not this also occurs with the newly re-added customized world type.

      Note that layers y=255 or below do work fine (MC-136526) while layers y=257 or above crash the editor due to MC-68124.

      Crash report

      From 1.13.2
      Description: Exception generating new chunk
      java.util.concurrent.CompletionException: java.lang.ClassCastException: bcd cannot be cast to ben
      	at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:273)
      	at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:280)
      	at java.util.concurrent.CompletableFuture.uniApply(CompletableFuture.java:604)
      	at java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:577)
      	at java.util.concurrent.CompletableFuture$Completion.exec(CompletableFuture.java:443)
      	at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
      	at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
      	at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
      	at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
      Caused by: java.lang.ClassCastException: bcd cannot be cast to ben
      	at ti.f(SourceFile:196)
      	at bxb.a(SourceFile:507)
      	at bxb.a(SourceFile:450)
      	at bxh$j.a(SourceFile:1764)
      	at bxc.a(SourceFile:62)
      	at btl.a(SourceFile:78)
      	at bvq.a(SourceFile:16)
      	at bvq.a(SourceFile:13)
      	at bpn.a(SourceFile:27)
      	at ayu.a(SourceFile:504)
      	at bop.a(SourceFile:183)
      	at tr.a(SourceFile:12)
      	at tq.a(SourceFile:35)
      	at bnd.a(SourceFile:95)
      	at tx.a(SourceFile:79)
      	at tx.a(SourceFile:25)
      	at acu$a.a(SourceFile:147)
      	at java.util.concurrent.CompletableFuture.uniApply(CompletableFuture.java:602)
      	... 6 more

            Unassigned Unassigned
            pokechu22 [Mod] Pokechu22
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