Consider reporting deprecation and feature warnings by default

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scalac does this, and a similar one for -feature:
"there were 2 deprecation warning(s); re-run with -deprecation for details"

When using sbt or Actiavtor, It's fairly involved (especially for newcomers to Scala) to figure out how to get the warning enabled. They aren't running scalac by hand so where and what do you "re-run with -deprecation."

I think the motivation for current behavior of scalac is to follow what javac does. The ticket is here to investigate if we want to flip the default for Scala 2.12.x.

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Imported From: https://issues.scala-lang.org/browse/SI-8829?orig=1
Reporter: @gkossakowski
See #6307

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@xeno-by said:
Discussion: https://groups.google.com/forum/#!topic/scala-internals/iny_QGKfuXc

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@SethTisue said:
+1. could have sworn I opened a ticket on this years ago, but apparently not. I've certainly randomly bitched about it a lot :-)

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@gkossakowski said:
@SethTisue, maybe organize Twitter campaign to vote on this issue? I think votes would help us to decide quickly on this :-)

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@SethTisue said:
https://twitter.com/SethTisue/status/505443243665137668

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@SethTisue said:
it's especially annoying in the REPL. that's when I really want to throttle it.

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Konrad Malawski (konrad.malawski) said:
+1-ed, and here's a tip for "the mean time", as when using sbt you can type printWarnings to get these warnings printed AFAIK: http://www.scala-sbt.org/0.13.5/docs/Howto/logging.html#printwarnings very useful but sometimes overlooked feature of sbt :-)

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@paulp said:
I almost feel bad telling you about this now if you've been sublimating throttle feelings toward the repl.

scala> Pair(1, 2)
warning: there was one deprecation warning; re-run with -deprecation for details
res0: (Int, Int) = (1,2)

scala> :warnings
<console>:8: warning: object Pair in object Predef is deprecated: Use built-in tuple syntax or Tuple2 instead
              Pair(1, 2)
              ^

It's been in there about three years. Sorry there's no indication when a warning is suppressed.

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@som-snytt said (edited on Sep 1, 2014 8:11:23 PM UTC):
This isn't quite as poignant, but:

scala> Pair(1,2)
warning: there was one deprecation warning; re-run with -deprecation for details
res0: (Int, Int) = (1,2)

scala> :settings +deprecation

scala> Pair(1,2)
<console>:8: warning: object Pair in object Predef is deprecated: Use built-in tuple syntax or Tuple2 instead
              Pair(1,2)
              ^
res1: (Int, Int) = (1,2)

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@puffnfresh said:
The sad thing is that when the -deprecation flag is not enabled, -Xfatal-warnings fails:

#8410

Which is pretty useless, since it offers no way to fix it until you enable the flag.

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@lrytz said:
un-scheduling from 2.12 - someone that feels strongly about it could submit a PR to spawn a discussion.

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@som-snytt said:
I was actually going to submit for REPL, where it seems like a no-brainer. Since the settings can be turned off now, the case can be made for scalac, although the default will be different when compiling cross-versions.

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@som-snytt said:
Only for REPL if neither option is set or unset by user:
scala/scala#5272

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@adriaanm said:
The REPL part is fixed for 2.12.0-RC1 by the above PR.