# Scala 3.9.0-RC6

- Product: Scala (https://whatsnew.fyi/product/scala)
- Vendor: Scala Center
- Date: 2026-08-19
- Version: 3.9.0-RC6
- Original notes: https://github.com/scala/scala3/releases/tag/3.9.0-RC6
- Permalink: https://whatsnew.fyi/product/scala/releases/3.9.0-rc6
- Labels: Pre-release

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **fixed** — Revert #26579 and #25126 for binary compatibility
- **fixed** — Preserve GADT constraints until PatternMatcher
- **fixed** — Ignore @throws annotation on non-methods
- **fixed** — Box bounded arguments of HKT result types in Java generic signatures
- **fixed** — Fix issue with reading legal java cyclic signatures
- **fixed** — Bail out of patDef opt for .runtimeChecked, not only @unchecked
- **fixed** — Do not emit Java generic signatures for trait private val setters
- **fixed** — Avoid patdef optimization for lazy vals in desugaring
- **fixed** — Fix variable expansion in Scaladoc

#### Backported changes

- Revert #26579 and #25126 for binary compatibility [#26813](https://github.com/scala/scala3/pull/26813)
- Preserve GADT constraints until PatternMatcher [#26805](https://github.com/scala/scala3/pull/26805)
- Ignore `@throws` annotation on non-methods [#26802](https://github.com/scala/scala3/pull/26802)
- Box bounded arguments of HKT result types in Java generic signatures [#26787](https://github.com/scala/scala3/pull/26787)
- Fix issue with reading legal java cyclic signatures [#26775](https://github.com/scala/scala3/pull/26775)
- Bail out of patDef opt for .runtimeChecked, not only `@unchecked` [#26774](https://github.com/scala/scala3/pull/26774)
- Do not emit Java generic signatures for trait private val setters [#26633](https://github.com/scala/scala3/pull/26633)
- Desugaring: avoid patdef optimization for lazy vals [#26770](https://github.com/scala/scala3/pull/26770)
- Scaladoc: Fix variable expansion [#26730](https://github.com/scala/scala3/pull/26730)


#### Contributors

Thank you to all the contributors who made this release possible 🎉

According to `git shortlog -sn --no-merges 3.9.0-RC6..3.9.0-RC6` these are:

```
     7	Wojciech Mazur
     6	Patryk Zieliński
     4	Solal Pirelli
     2	Jan Chyb
     1	Rikito Taniguchi

```