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SethTisue /
Last active Sep 10, 2019
Scala 2.12.10 release notes (DRAFT)


The main purpose of this release is to fix the following regressions in 2.12.9:

  • Fix regression in large string interpolations with non-String typed splices (#8315)
  • Revert "Generate shallower ASTs in pattern translation" (#8327, reverting #8061)
  • Fix regression in classpath when JARs have 'a.b' entries beside 'a/b' (#8321)

Further highlights


Fixes with compatibility implications

Scala 2.12.9 generates shallower ASTs in pattern translation, to reduce stack size requirements (-Xss) during compilation.

Scala.js users must update to 0.6.28+ or 1.0.0-M8+ for compatibility with Scala 2.12.9. (#7375)

Highlights of 2.12.9

  • Improved compatibility with JDK 11, 12, and 13 (see below)
SethTisue /
Last active Jun 19, 2019
chaining implicit conversions in Scala 2 and Scala 3

in Scala 2, they don't chain 😇, even if we try to give the compiler an assist

can we make them chain in Dotty? 😈

let's try it!

first let's set up sbt:

% cat project/plugins.sbt
SethTisue /
Last active May 17, 2019
Scala 2.13.0-RC2 draft release notes
SethTisue /
Last active Apr 5, 2019
Scala 2.13.0-RC1 draft release notes
SethTisue /
Last active Aug 28, 2018
Scala 2.13.0-M5 draft release notes

Scala 2.13 is getting closer and closer!

We've been polishing the improved and simplified Scala collections library that first shipped in 2.13.0-M4. We expect the API to remain stable now, though there may still be minor changes in RC1.

M5 is our feature-freeze release for 2.13. From here forward, we’ll close existing open loops but not embark on or accept new work.

Collections changes

The major collections changes already landed in M4. See the M4 release notes for a summary.


(excerpts from emails I sent my co-workers at Northwestern University)

January 2008

Did some reading on Scala, Groovy, and JRuby. I'm interested in adding another language to the devel team's repertoire, a JVM-based language that interoperates smoothly with Java code so we could write new code in the new language without being forced to change existing code. I'm particularly interested in having a more powerful language than Java to use for

View gist:4bd5f2e8c2f9d11031c93f259937eeb3
Welcome to Scala 2.12.4 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_131).
Type in expressions for evaluation. Or try :help.
scala> :power
Power mode enabled. :phase is at typer.
import,, definitions._
Try :help or completions for vals._ and power._
scala> println(nodePrinters.nodeToString(reify { List(1, 2, 3).map(_ * 2) }.tree))
View array-view
scala> Array("a", "b", "c", "d")
res0: Array[String] = Array(a, b, c, d)
scala> res0.view.slice(1, 3)
res1: scala.collection.mutable.IndexedSeqView[String,Array[String]] = SeqViewS(...)
scala> res1.toList
res2: List[String] = List(b, c)
scala> res1(0) = "zzz"
SethTisue / 7234.txt
Created Jun 26, 2017
is this scala/bug#7234 or something else?
View 7234.txt
scala> trait T; class C[T2 <: T](val t: T2, b: Boolean = true, n: Int = 0)
defined trait T
defined class C
scala> val t = new T { }
t: T = $anon$1@f2a1813
scala> new C[t.type](t)
res0: C[<refinement>.type] = C@7645f03e
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