Some suggestions about Scala script example

[counter2015]

In the doc website: https://www.scala-lang.org/documentation/your-first-lines-of-scala.html

It shows a example of Scala script.

#!/usr/bin/env scala

object HelloWorld extends App {
  println("Hello, world!")
}
HelloWorld.main(args)

When I try to run it, the compiler returns a warning.

$ ./script.sh 
./script.sh:6: warning: Script has a main object but statement is disallowed
HelloWorld.main(args)
               ^
Hello, world!

In fact without HelloWorld.main(args), it can also run while has access to args

#!/usr/bin/env scala

object HelloWorld extends App {
  println(s"Hello, world! ${args.mkString}")
}

$ ./script.sh Hello, Scala Script
Hello, world! Hello,ScalaScript

On the other hand, I found another Scala shell script example

In this one I can pass Scala comand line arguement such as -feature

#!/bin/sh
exec scala -feature -deprecation "$0" "$@"
!#

object Test {
  def main(args: Array[String]): Unit = {
    implicit def strToSymbol(str: String): Symbol = Symbol(str)
    println("hello, world")
  }
}

In this way, it will show me details about warning.

$ ./test.scala 
./test.scala:7: warning: implicit conversion method strToSymbol should be enabled
by making the implicit value scala.language.implicitConversions visible.
This can be achieved by adding the import clause 'import scala.language.implicitConversions'
or by setting the compiler option -language:implicitConversions.
See the Scaladoc for value scala.language.implicitConversions for a discussion
why the feature should be explicitly enabled.
    implicit def strToSymbol(str: String): Symbol = Symbol(str)
                 ^
hello, world

In my humble opinion, I have two suggestions:

• Remove HelloWorld.main(args) from the example since it will cause a warning.
• Using second header of script header since it can pass command line arguements of Scala.

[SethTisue]

Agree on both counts. Pull requests highly welcome.

[counter2015]

@SethTisue Thanks for your reply. I have made a PR here.