Compiler flags for literal types?

[davegurnell]

Reported by @d6y:

Box on "Literal types in Scala", p. 56

There's a flag to enable this stuff, right? Worth saying that?

As of Lightbend Scala....., with the -wibble flag enabled, we now have direct syntax support...

[metasim]

The example

val theAnswer: 42 = 42

does not work in (non-Typelevel) Scala 2.11.11 nor 2.12.3.

scala> val theAnswer: 42 = 42
<console>:1: error: identifier expected but integer literal found.
       val theAnswer: 42 = 42
                      ^

According to the callout on p56 it should, right?

[davegurnell]

Do you have scalacOptions += "-Yliteral-types" in your build.sbt? I think you need to enable that for literal types. I can't remember how much I go into this stuff in the book, but I wouldn't be surprised if it wasn't clear enough.

On Thu, Sep 7, 2017 at 6:37 PM Simeon H.K. Fitch [email protected] wrote:

The example

val theAnswer: 42 = 42

does not work Lightbend 2.11.11 nor 2.12.3.

scala> val theAnswer: 42 = 42 :1: error: identifier expected but integer literal found. val theAnswer: 42 = 42 ^

According to the callout on p56 it should, right?

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[metasim]

When I posted that I was looking at the PDF version at work. At home I have the paperback version, and noted there that it does reference the -Yliteral-types flag. So it looks like the Lulu version is more up to date than the free PDF version.

All that said, this is what I'm getting with 2.12.3:

sfitch$ scalac -version
Scala compiler version 2.12.3 -- Copyright 2002-2017, LAMP/EPFL and Lightbend, Inc.
sfitch$ scalac -Yliteral-types
scalac error: bad option: '-Yliteral-types'
  scalac -help  gives more information

[davegurnell]

Thanks for the update. I'll look into the book text in a next set of updates.

I'm guessing 2.12.3 may have -Yliteral-types enabled by default?

On Fri, Sep 8, 2017 at 2:02 PM Simeon H.K. Fitch [email protected] wrote:

When I posted that I was looking at the PDF version at work. At home I have the paperback version, and noted there that it does reference the -Yliteral-types flag. So it looks like the Lulu version is more up to date than the free PDF version.

All that said, this is what I'm getting with 2.12.3:

sfitch$ scalac -version Scala compiler version 2.12.3 -- Copyright 2002-2017, LAMP/EPFL and Lightbend, Inc. sfitch$ scalac -Yliteral-types scalac error: bad option: '-Yliteral-types' scalac -help gives more information

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[metasim]

Nope:

sfitch$ scala -version
Scala code runner version 2.12.3 -- Copyright 2002-2017, LAMP/EPFL and Lightbend, Inc.

sfitch$ scala -Yliteral-types
bad option: '-Yliteral-types'

Usage: scala <options> [<script|class|object|jar> <arguments>]
   or  scala -help

All options to scalac (see scalac -help) are also allowed.

sfitch$ scala
Welcome to Scala 2.12.3 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_121).
Type in expressions for evaluation. Or try :help.

scala> val theAnswer: 42 = 42
<console>:1: error: identifier expected but integer literal found.
       val theAnswer: 42 = 42
                      ^

[d6y]

Update on this: it looks like the PR for literal types isn't yet merged into Lightbend Scala. Probably worth updating the text to say "...and coming soon in Lightbend Scala".

[davegurnell]

Thanks for this. I'll correct for the next version. To be honest I get confused as to what's available where. Too many updates! Still, it's a good problem to have :) On Fri, 15 Sep 2017 at 16:51, Richard Dallaway [email protected] wrote:

Update on this: it looks like the PR for literal types isn't yet merged into Lightbend Scala. Probably worth updating the text to say "...and coming soon in Lightbend Scala".

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