# Scala 3.8.4

- Product: Scala (https://whatsnew.fyi/product/scala)
- Vendor: Scala Center
- Date: 2026-06-05
- Version: 3.8.4
- Original notes: https://github.com/scala/scala3/releases/tag/3.8.4
- Permalink: https://whatsnew.fyi/product/scala/releases/3.8.4

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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- **added** — Allow :help syntax for all settings
- **added** — Add logical package parsing for sourcepath
- **changed** — Upgrade Scala CLI to 1.14.0
- **added** — Support for .test.java files in Scala CLI
- **added** — Toggle to turn auto-IDE-setup off in Scala CLI
- **added** — Cross support for run, package and doc sub-commands in Scala CLI (experimental)
- **added** — Global --offline config key in Scala CLI
- **added** — Local .m2 in publish local in Scala CLI (experimental)
- **added** — Support for Scala.js 1.21.0 in Scala CLI
- **added** — java-test-runner for pure Java tests in Scala CLI
- **added** — GraalVM native-image packaging support with packaging.graalvmJvmId and packaging.graalvmArgs in Scala CLI
- **deprecated** — Ammonite REPL in Scala CLI
- **fixed** — Copy param annotations at mixin
- **fixed** — Do not simplify isInstanceOf if unrelated types might be subtypes at run-time
- **changed** — Use Objects.equals in translating ==
- **fixed** — Fix crash when processing path dependent context functions using HKTs
- **fixed** — Preserve singleton precision during scoverage lifting
- **fixed** — Ensure package transformation properly handles language imports in InstrumentCoverage
- **changed** — Do not instrument erased values in scoverage
- **fixed** — Fix named arguments evaluation order with by-name parameters

#### Highlights of the release

- Allow `:help` syntax for all settings [#26052](https://github.com/scala/scala3/pull/26052)
- feature: Add logical package parsing for sourcepath [#25446](https://github.com/scala/scala3/pull/25446)
- Upgrade Scala CLI to 1.14.0
    * https://github.com/VirtusLab/scala-cli/releases/tag/v1.12.5
        * `--cross` support for run, package and doc sub-commands (experimental)
        * Global `--offline` config key
        * Local .m2 in publish local (experimental)
    * https://github.com/VirtusLab/scala-cli/releases/tag/v1.13.0
        * Support for Scala.js 1.21.0
        * Ammonite REPL deprecated & scheduled for removal
        * `java-test-runner` for pure Java tests
        * GraalVM native-image packaging: `packaging.graalvmJvmId` and `packaging.graalvmArgs`
    * https://github.com/VirtusLab/scala-cli/releases/tag/v1.14.0
        * Support for `.test.java`
        * A toggle to turn auto-IDE-setup off

#### Other changes and fixes

##### Annotations

- Also copy param annots at mixin [#24916](https://github.com/scala/scala3/pull/24916)
- Named arg may be deprecatedName [#21588](https://github.com/scala/scala3/pull/21588)
- Use `dealiasKeepRefiningAnnots` in `AvoidMap` [#25609](https://github.com/scala/scala3/pull/25609)

##### Backend

- Do not simplify isInstanceOf if unrelated types might be subtypes at run-time [#25535](https://github.com/scala/scala3/pull/25535)
- Port more Scala2 tests + some mixin improvements [#25573](https://github.com/scala/scala3/pull/25573)
- Use `Objects.equals` in translating `==` [#25314](https://github.com/scala/scala3/pull/25314)

##### Compiler Phases

- Harden Period creation and use of Run/PhaseId [#25484](https://github.com/scala/scala3/pull/25484)
- Make Phase.run protected [#25366](https://github.com/scala/scala3/pull/25366)

##### Context Functions

- Fix crash when processing path dependent context functions using HKTs [#25530](https://github.com/scala/scala3/pull/25530)

##### Coverage

- Fix #25555: Preserve singleton precision during scoverage lifting [#25556](https://github.com/scala/scala3/pull/25556)
- Fixes #25482: Ensure package transformation properly handles language imports in InstrumentCoverage [#25546](https://github.com/scala/scala3/pull/25546)
- Scoverage: do not instrument erased values. [#25298](https://github.com/scala/scala3/pull/25298)

##### Default parameters

- Fix named arguments evaluation order with by-name parameters [#25161](https://github.com/scala/scala3/pull/25161)
- Typer: remove by-name lifting and replace default-getter args with fresh syms [#25502](https://github.com/scala/scala3/pull/25502)

##### Documentation

- Error mentions bad _1 selector [#25616](https://github.com/scala/scala3/pull/25616)
- Document Scala compiler error codes [#24734](https://github.com/scala/scala3/pull/24734)
- Fix capture checking doc links in language.scala [#25498](https://github.com/scala/scala3/pull/25498)
- Docs: apply snippet compiler on new types reference docs [#19513](https://github.com/scala/scala3/pull/19513)
- Remove outdated comment in value classes [#25428](https://github.com/scala/scala3/pull/25428)
- Update `IsIterable` scaladoc [#24692](https://github.com/scala/scala3/pull/24692)

##### Enums

- Make enum apply ascriptions inferred types [#25562](https://github.com/scala/scala3/pull/25562)

##### Extension Methods

- Accept using right associative parameters [#24766](https://github.com/scala/scala3/pull/24766)
- Better handling of illegal trees in `extension` [#25368](https://github.com/scala/scala3/pull/25368)

##### GADTs

- Also trust TypeTest when there is a Bind [#24568](https://github.com/scala/scala3/pull/24568)

##### Implicits

- Deprecation when inferring implicit from non-accessible companion [#25516](https://github.com/scala/scala3/pull/25516)
- Fix missing deprecation warning for implicit in non-accessible companion [#25608](http

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