Why does a large array constructor call break the Scala compiler?

Question

I'm doing some image processing for a job and was scripting things with Im4Java. In order to write some unit cases I decided to just store a local image as a byte array in the code. I grabbed a simple test image

And then converted it to the byte array like so:

import java.nio.file.{Paths, Files}
import java.nio.charset.StandardCharsets
val stuff =scala.io.Source.fromFile(fileName)(scala.io.Codec.ISO8859).map(_.toByte).toArray
Files.write(Paths.get("tmp.txt"), stuff.mkString(",").getBytes(StandardCharsets.UTF_8))

And then put those bytes into an Array[Byte] apply constructor:

class testCase() {
    val smallFile = Array[Byte](-1,-40,-1, …) // 9816 arguments to the constructor passed here
}

When I tried to compile this (see the full scala file in this gist) I was surprised to see it break the compiler's typer! I get the following stacktrace (I've truncated it a bit):

[error] uncaught exception during compilation: java.lang.StackOverflowError
java.lang.StackOverflowError
at scala.reflect.internal.Symbols$Symbol.info(Symbols.scala:1241)
at scala.reflect.internal.Symbols$Symbol.baseTypeSeqLength$1(Symbols.scala:1628)
at scala.reflect.internal.Symbols$Symbol.isLess(Symbols.scala:1631)
at scala.reflect.internal.Types$Type.baseTypeIndex(Types.scala:992)
at scala.reflect.internal.Types$CompoundType.baseType(Types.scala:1655)
at scala.reflect.internal.Types$ClassTypeRef$class.baseType(Types.scala:2186)
at scala.reflect.internal.Types$TypeRef$$anon$6.baseType(Types.scala:2544)
at scala.reflect.internal.Types$class.firstTry$1(Types.scala:6064)
at scala.reflect.internal.Types$class.isSubType2(Types.scala:6228)
at scala.reflect.internal.Types$class.isSubType(Types.scala:5837)
at scala.reflect.internal.SymbolTable.isSubType(SymbolTable.scala:13)
at scala.reflect.internal.Types$class.fourthTry$1(Types.scala:6223)
at scala.reflect.internal.Types$class.thirdTryRef$1(Types.scala:6123)
at scala.reflect.internal.Types$class.thirdTry$1(Types.scala:6145)
at scala.reflect.internal.Types$class.secondTry$1(Types.scala:6109)
at scala.reflect.internal.Types$class.firstTry$1(Types.scala:6070)
at scala.reflect.internal.Types$class.isSubType2(Types.scala:6228)
at scala.reflect.internal.Types$class.isSubType(Types.scala:5837)
at scala.reflect.internal.SymbolTable.isSubType(SymbolTable.scala:13)
at scala.reflect.internal.Types$Type.$less$colon$less(Types.scala:872)
at scala.tools.nsc.typechecker.Typers$Typer.adapt(Typers.scala:1091)
at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5660)
at scala.tools.nsc.typechecker.Typers$Typer.typedArg(Typers.scala:3042)
at scala.tools.nsc.typechecker.Typers$Typer.loop$1(Typers.scala:3069)
at scala.tools.nsc.typechecker.Typers$Typer.loop$1(Typers.scala:3071)
at scala.tools.nsc.typechecker.Typers$Typer.loop$1(Typers.scala:3071)
at scala.tools.nsc.typechecker.Typers$Typer.loop$1(Typers.scala:3071)
at scala.tools.nsc.typechecker.Typers$Typer.loop$1(Typers.scala:3071)
at scala.tools.nsc.typechecker.Typers$Typer.loop$1(Typers.scala:3071)
(etc as this is where the stackoverflow happens)

I'm using the Scala 2.10.5 compiler and java jdk1.7.0_79

I'm probably going to just use a smaller image or something to fix my issue, but I would like to know why the compiler does this and if it can be fixed?

Answer 1

Well I tried to reproduce your problem and newer scalac (2.11.7) has a better error message (hope it clears up the problem):

» scalac Arrays.scala
Arrays.scala:1: error: Could not write class testCase because it exceeds JVM code size limits. Method <init>'s code too large!
class testCase()  {
      ^
one error found

So it looks like, just like @Marius noted in comments, you're hitting "64K bytecode per method" limit imposed by JVM.