Highlights of the release

Bump Scala CLI to 1.12.5 and Coursier to 2.1.25-M24 #25592

Other changes and fixes

Annotations

Also copy param annots at mixin #24916
Named arg may be deprecatedName #21588
Use dealiasKeepRefiningAnnots in AvoidMap #25609

Backend

Do not simplify isInstanceOf if unrelated types might be subtypes at run-time #25535
Port more Scala2 tests + some mixin improvements #25573
Use Objects.equals in translating == #25314

Compiler Phases

Harden Period creation and use of Run/PhaseId #25484
Make Phase.run protected #25366

Context Functions

Fix crash when processing path dependent context functions using HKTs #25530

Coverage

Fix #25555: Preserve singleton precision during scoverage lifting #25556
Fixes #25482: Ensure package transformation properly handles language imports in InstrumentCoverage #25546
Scoverage: do not instrument erased values. #25298

Default parameters

Fix named arguments evaluation order with by-name parameters #25161
Typer: remove by-name lifting and replace default-getter args with fresh syms #25502

Documentation

Error mentions bad _1 selector #25616
Document Scala compiler error codes #24734
Fix capture checking doc links in language.scala #25498
Docs: apply snippet compiler on new types reference docs #19513
Remove outdated comment in value classes #25428
Update IsIterable scaladoc #24692

Enums

Make enum apply ascriptions inferred types #25562

Experimental: Capture Checking

Distribute capture set into and-type on RHS of comparison #25509
Fix global capabilities support in scaladoc #25563
Improve capture-error precision for lambdas #25583
Make result types of hoisted superArg defs InferredTypes #25577
Transform result any to fresh in Setup.transformSym #25584
Propagate expected types when rechecking match return expressions #25580
Drop assertion in toFunctionType #25628
Delay normalization of capture sets of vals and defs #25640
Fluidify explicit self types for non-CC classes #25639
Add missing TypeMap in Setup: FreshCapToResult #25648
Fixes for capture checking case class methods #25278
Don't add capture variables for type arguments with pure upper bounds #25316
Two fixes for #25251 #25488
Fixed #25430: Add missing CaptureChecked flag during ExpandSAMs #25443
Fix accessibility check for any's in static objects #25582
Disallow type parameters in OnlyCapability annotations #25496
Capture check Try #25072
Make Capability types have implied capture sets for new #25346

Experimetnal: Safe Mode

Enhance safe mode #25638
Fixes to Safe Mode Checking #25603

Extension Methods

Accept using right associative parameters #24766
Better handling of illegal trees in extension #25368

GADTs

Also trust TypeTest when there is a Bind #24568

Implicits

Deprecation when inferring implicit from non-accessible companion #25516
Fix missing deprecation warning for implicit in non-accessible companion #25608
Update migration message #25627

Inline

Enhance constant-folding during inlining #24431
Ensure the inline match scrutinee type conforms to the recalculated type #24988
Do not update Symbol defTrees when retyping after Inlining #23870
Inlines: decide sealing against original target, while using widened type as cast destination #25448
Do not generate access proxies for locally defined protected defs #25056
Avoid useless scrutinee proxy vals in inline match reduction #25279

Linting

Match apply in PolyFunction for override #25505
Value discard checks inline call for exemption #25554
Introduce error message ids for shadow warnings #25101

Match Types

Restore MatchTypeNoCases warning with correct source position #25470

Named Tuples

Fix Ycheck crash from singleton tuple selects after specialization #25331
Fix #23621: make named tuples exhaustive checkable #25267

Nullability

Patch to allow interop with XMLBuilder and -Yexplicit-nulls #25221
Be honest about the nullability of ConsoleReporter.reader and SourcePosition.outer. #25561

Opaque Types

Treat synthetic casts as pure #25126

Overloading

Pretype args before skipping clause of overloaded application #23012

Parser

Fix #20063: Java leading annotation parsing #25503
Observe outdent also for type cases and type blocks in quotes #25519
Fix: import resolution for Java #25537
Fix #25456: parser crash on polymorphic context bound #25623
Accept primitive.class in annotations #25363
InCase has indent width of case #25295
Don't automatically insert OUTDENT before COMMA #25501
Add "did you mean to use parentheses/a block" when finding a complex expression on the RHS of an infix operator #25099

Pattern Matching

Clean desugaring of simple tuple assignments #25010
Extend caching in the space engine beyond local context #23483
Prevent from getting children in case of non-sealed private #25359
Use MatchCaseUnreachable #24829
Fix wrong exhaustive check with sequence wildcard on case class with custom unapply #24260
Try expanding case class to the product of its fields #25454

Positions

Preserve span of this during statification of trait constructors #25354

Presentation Compiler

Improvement: Add fallbacks in non critical places for presentation compiler #25483
Improvement: Use method type if it's available #25641
Bugfix: Fix wrong type in InferredType code action #25469
Fix & feat: improvements in selection ranges #25290
Fix: ignore implicit apply for signature help #25294
Bugfix: remove stale top-level symbols between runs #25317

Quotes

Fix crashing for context bound type variables in quoted patterns #25286
Remove redundant mapOver in fixThisTypeModuleClassReferences #25440

Reflection

Fix Select.copy in reflect API losing DerivedName for default getters #25269
Do not expose ClassInfo in memberType in reflect API #24922

Reporting

Force conditional warnings when configured #25552
Suppressions before finalize #25576
Use dollar-free param names in stub implementations #25646
Fix #24711: Use dot notation for Java nested types in error messages #24919
Use deprecatedOverriding message #25439
Improve message for misplaced using #15624
Use other tree for actual symbol of Assign #22869

REPL

Allow global language imports in REPL and snippet compiler #25458
Fix all REPL tests when production behavior is enabled #25449
Add setting to control REPL print height #25560

Rewrites

Fix incorrect rewrite of expr _ when expr has a function type #25457

Runner

Fix for #22443: prevent stty from being called when not running in a terminal #22444

Scala.js

Fix #25342: Transfer methodsAllowingJSAwait to forcefully inlined methods. #25344

Scaladoc

Use <sup> tags for exponents in Scaladoc comments #25645
Do not hide when a class or a trait extends Any #25403
Do not generate documentation for AnyVal, it exists now #25399
Ability to hide snippets from the documentation #25411
Update scaladoc signature for given methods #25325
Fetch the right kind for synthesised definitions #25405
Scaladoc: Take title from sidebar.yml into account #18997

SemanticDB

Encapsulate SemanticDB package, unify symbol and document printing #25084
Better refinement symbols in semanticDB #18604

Standard Library

Array.range trusts NumericRange.count #24878
Chore: optimize lazy val with power of two. #22428

Syntax

Check protected parent constructor accesses only occurs in child constructors #25511
Fix protected constructor access #25523

Tooling

Fix MSI installer reporting wrong Scala version on Windows #25591

Transform

Always encode <init> in derived name #23478

Tuples

Normalize tuple types when typing patterns #25335
Rewrite Desugar.makePatDef to fix typing issues and be more understandable #24972

Typeclass Derivation

Fix #23043: spurious package conflict from non-class directories #25441
Also checkRefinement for Singleton mirror #24080

Typer

Preserve pattern, use tuple type when optimizing #25566
Detect InsertedApply on Apply to break synthetic apply loops, not just Select #25463
Fail self-recursive deferred given impl #22595
Use TypeComparer.constValue in TypeEval #24718
Add the transparent flag to java.lang.Object #25394

Contributors

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

According to git shortlog -sn --no-merges 3.8.3..3.8.4-RC1 these are:

    87	Solal Pirelli
    67	Martin Odersky
    31	Som Snytt
    12	Hamza Remmal
    10	Matt Bovel
     9	Oliver Bračevac
     9	Wojciech Mazur
     8	Jan Chyb
     8	Piotr Chabelski
     8	Rikito Taniguchi
     8	Tomasz Godzik
     8	dependabot[bot]
     7	Yichen Xu
     7	noti0na1
     6	Jakub Warchoł
     5	Emil Ejbyfeldt
     4	Kenji Yoshida
     3	Anatolii Kmetiuk
     3	HarrisL2
     3	Lukas Rytz
     3	Sébastien Doeraene
     2	110416
     2	James You
     2	Matt Dziuban
     2	Ondřej Lhoták
     2	Patryk Zieliński
     2	Ruslan Shevchenko
     1	Aviral Garg
     1	Bbn08
     1	Eugene Flesselle
     1	Harrishan Raveendran
     1	He-Pin(kerr)
     1	Jakub Cieśluk
     1	Jeon Yoonjae
     1	Li Haoyi
     1	Mark Hammons
     1	Natsu Kagami
     1	Oliver Marienfeld
     1	Piotr Paradziński
     1	Vadim Chelyshov
     1	philwalk