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  1. class Box[+A] {
  2.  
  3.   def set(x : A) : Box[A]
  4.  
  5. } // won't compile
Compilation error #stdin compilation error #stdout 0s 0KB
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stdin
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Standard input is empty
compilation info 
/opt/scala/bin/scalac: line 50: /dev/null: Permission denied
Main.scala:1: error: class Box needs to be abstract, since method set is not defined
class Box[+A] {
      ^
Main.scala:3: error: covariant type A occurs in contravariant position in type A of value x
  def set(x : A) : Box[A]
          ^
two errors found
spoj: The program compiled successfully, but Main.class was not found.
      Class Main should contain method: def main(args: Array[String]).
stdout
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Standard output is empty
https://ideone.com/xOHVs7
language:
Scala (scala 2.12.8)
created:
9 years ago
visibility:
public

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