unhandled exception while running MegaPhase

[philwalk]

Compiler version

# scala -version
Scala code runner version 3.4.0-RC1 -- Copyright 2002-2023, LAMP/EPFL

# java -version
openjdk version "19" 2022-09-20
OpenJDK Runtime Environment (build 19+36-2238)
OpenJDK 64-Bit Server VM (build 19+36-2238, mixed mode, sharing)

Minimized code

The scala script below crashes the compiler if called as described.
Name the script ./vsortBug.sc and attempt to run it with this bash script:

#!/bin/bash

SCALA_HOME="C:/opt/scala3-3.4.0-RC1"
PATH="$SCALA_HOME/bin:$PATH"

echo "-cp C:/opt/scala3-3.3.1/lib/scala3-library_3-3.3.1.jar" > bugAtfile
SCALA_OPTS=@bugAtfile ./vsortBug.sc

I have a classpath @file with dozens of entries, and I eventually discovered a compiler lib file from an incompatible version, scala3-library_3-3.3.1.jar towards the end, so this is not a compiler bug, although it might be worthwhile to immunize against this category of bug somehow.

It's not surprising that launching the script with scala3-3.4.0-RC1 leads to a crash, although it took awhile to figure out root cause.

Possible fixes: when incompatible compiler jars appear in the classpath:

• issue warnings
• filter them out
• replace them with correctly versioned equivalents
• close this issue with no changes

If the runtime version scala3-library_3-3.4.0-RC1.jar appears earlier in the classpath, no crash.

#!/usr/bin/env -S scala

object VersionSort {

  def main(_args: Array[String]): Unit =
    println("hello")

  case class PathString(path: String) extends Ordered[PathString] {
    val fields = path.split("[\\D]+").toList.map {
      case num if num.trim.matches("[0-9]+") => "%010f".format(num.toDouble)
      case str => str
    } // .mkString("| ")
    //printf("%s [%s]\n", path, fields.mkString("|"))
    override def toString = path

    // compare subfields fields
    def compare(other: PathString): Int = {
      var i = 0
      val of = other.fields
      val tf = this.fields
      val maxindex = of.size.min(tf.size) -1
      var num = 0
      while (i <= maxindex && num == 0) {
        num = tf(i) compare of(i)
        i += 1
      }
      num
    }
  }
}

Output (click arrow to expand)

When the classpath

echo "-cp C:/Users/philwalk/AppData/Local/https/repo1.maven.org/maven2/org/scala-lang/scala3-library_3/3.3.1/scala3-library_3-3.3.1.jar" > bugAtfile

SCALA_OPTS=@bugAtfile jsrc/vsortBug.sc 2>&1 | tee s124

  unhandled exception while running MegaPhase{protectedAccessors, extmethods, uncacheGivenAliases, elimByName, hoistSuperArgs, forwardDepChecks, specializeApplyMethods, tryCatchPatterns, patternMatcher} on C:\opt\ue\jsrc\vsortBug.sc

  An unhandled exception was thrown in the compiler.
  Please file a crash report here:
  https://github.com/lampepfl/dotty/issues/new/choose
  For non-enriched exceptions, compile with -Yno-enrich-error-messages.

     while compiling: C:\opt\ue\jsrc\vsortBug.sc
        during phase: MegaPhase{protectedAccessors, extmethods, uncacheGivenAliases, elimByName, hoistSuperArgs, forwardDepChecks, specializeApplyMethods, tryCatchPatterns, patternMatcher}
                mode: Mode(ImplicitsEnabled)
     library version: version 2.13.12
    compiler version: version 3.4.0-RC1
            settings: -classpath C:/Users/philwalk/AppData/Local/https/repo1.maven.org/maven2/org/scala-lang/scala3-library_3/3.3.1/scala3-library_3-3.3.1.jar;C:/opt/scala/lib/scala-library-2.13.12.jar;C:/opt/scala/lib/scala3-library_3-3.4.0-RC1.jar;C:/opt/scala/lib/scala-asm-9.6.0-scala-1.jar;C:/opt/scala/lib/compiler-interface-1.9.3.jar;C:/opt/scala/lib/scala3-interfaces-3.4.0-RC1.jar;C:/opt/scala/lib/scala3-compiler_3-3.4.0-RC1.jar;C:/opt/scala/lib/tasty-core_3-3.4.0-RC1.jar;C:/opt/scala/lib/scala3-staging_3-3.4.0-RC1.jar;C:/opt/scala/lib/scala3-tasty-inspector_3-3.4.0-RC1.jar;C:/opt/scala/lib/jline-reader-3.19.0.jar;C:/opt/scala/lib/jline-terminal-3.19.0.jar;C:/opt/scala/lib/jline-terminal-jna-3.19.0.jar;C:/opt/scala/lib/jna-5.3.1.jar -d C:\tmp\scala3-scripting10473104943302070702

Exception in thread "main" dotty.tools.dotc.core.TypeError$$anon$1: object caps does not have a member type Cap

[nicolasstucki]

@odersky It is failing on object caps does not have a member type Cap did something change there recently?

[nicolasstucki]

We might be trying to read caps.Cap on a version that still has caps.Root (see 803e06a).

[nicolasstucki]

In general, we should not be using the 3.3 library with 3.4 compiler. We should check this when we load the compiler.