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Last active March 11, 2020 10:10
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draft release notes for Scala 2.12.11

Collections fixes

  • Fix 2.12-only bug where some toX methods could expose the underlying mutability of a ListBuffer-generated collection (#8674)

(The release includes other collections bugfixes, but this one is especially notable.)

Java interoperability

Assorted small improvements to handling of Java sources (thanks @hrhino).

JDK compatibility

  • Make optimizer work on JDK 13+ (#8676)
  • Make :javap work in the REPL on JDK 9+ (#8400)

REPL changes

  • Improve -Yrepl-class-based (#8712)
  • -Yrepl-use-magic-imports avoids nesting $iw wrappers (#8576)

(TODO need much better descriptions)


  • further improved thread safety of runtime reflection (#8433) and fixed a memory leak introduced in 2.12.10 (#8470)


  • assorted compilation performance improvements
    • (need an overall compiler benchmark number from Jason)
  • assorted collections performance improvements

standard library changes

  • Duration strings now support "m" for minutes and "hr" for hours (#8325, #8450)

compiler plugins changes

  • -Xpluginsdir works again (it regressed in 2.12.9) (#8542)
  • compiler phase ordering is now deterministic in more cases (#8427)

changes relevant to build pipelining (?)

  • Add a mode to write separate .sig files without really private members (#8556)
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lrytz commented Mar 11, 2020

todo: mention scala/scala-dev#675

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