Highlights of the release

• Bump JLine 3.19.0 -> 3.24.1 & sbt 1.9.7 -> 1.9.9 #19744
• Refactor settings & improve dx #19766
• Publish scala2-library-tasty-experimental #19588
• Repl - method signatures in autocomplete #19917

Other changes and fixes

Annotations

• Attempt implicit search for old style implicit parameters in Application matchArgs #19737

Backend

• Fix(#17255): cannot find Scala companion module from Java #19773
• Change isStatic to isStaticOwner in hasLocalInstantiation #19803

Coverage

• Port coverage filter options for packages and files #19727

Default parameters

• Lift all non trivial prefixes for default parameters #19739

Doctool

• Prevent HTML/XSS Injection in Scala Search #19980
• Parse search query param in Scaladoc #19669

Experimental: Capture Checking

• Disallow covariant caps in the lower bound of type members #19624
• Ignore orphan parameters inside a retains annotation during Ycheck #19684
• Fix the pickling of This inside capture sets #19797
• Add updated to SeqViewOps #19798
• Fix Function tree copier #19822
• Drop FreeSeqFactory from stdlib-cc #19849
• Fix i19859 #19860
• Various fixes to stdlib-cc #19873
• Add more methods in SeqViewOps #19993
• Check This references in refersToParamOf #20005

Exports

• Fix the tparam bounds of exported inherited classes #18647

Implicits

• Prefer extensions over conversions for member selection #19717
• Don't allow implicit conversions on prefixes of type selections #19934
• Make sure typeParams returns a stable result even in the presence of completions #19974

Incremental Compilation

• Fix undercompilation upon ctor change #19911
• Load but not enter case accessors fields in Scala2Unpickler #19926

Initialization

• Add supports for type cast and filtering type for field and method owner in global initialization checker #19612
• Added a second trace for global init checker showing creation of mutable fields #19996
• Suppressing repetitive warnings in the global initialization checker #19898

Inline

• Specialized retained inline FunctionN apply methods #19801
• Avoid crash after StopMacroExpansion #19883
• Check deprecation of inline methods #19914
• Inline transparent implicit parameters when typing Unapply trees #19646
• Restore pre-3.3.2 behavior of inline implicit def #19877

Match Types

• Cover patterns using reflect.TypeTest in isMatchTypeShaped #19923
• Rework MatchType recursion in collectParts #19867

Nullability

• Fix #19808: Don't force to compute the owner of a symbol when there is no denotation #19813

Parser

• Add support for JEP-409 (sealed classes) + Add javacOpt directive #19080
• Fix(#16458): regression in xml syntax parsing #19522
• Fix parsing of conditional expressions in parentheses #19985

Presentation Compiler

• Allow range selection on function parameter to select a parameter list #19777

Quotes

• Disallow ill-staged references to local classes #19869
• Add regression test for #19909 #19915
• Detect non Expr[..] splice patterns #19944
• Avoid spurious val binding in quote pattern #19948
• Add regression test and imporve -Xprint-suspension message #19688

REPL

• Repl truncation copes with null #17336
• Catch stackoverflow errors in the highlighter #19836
• Fix a REPL bad symbolic reference #19786

Reflection

• Fix TypeTreeTypeTest to not match TypeBoundsTrees #19485
• Improve message when tree cannot be shown as source #19906
• Fix #19732: quotes.reflect.Ref incorrectly casting This to RefTree #19930
• Add check for parents in Quotes (#19842) #19870

Reporting

• Improve error reporting for missing members #19800
• Avoid repetitions in name hints #19975
• Improve error message when using experimental definitions #19782
• Make -Xprompt work as desired under -Werror #19765
• Fix #19402: emit proper error in absence of using in given definitions #19714
• Bugfix: Choose correct signature is signatureHelp for overloaded methods #19707
• Unify completion pos usage, fix presentation compiler crash in interpolation #19614

Scaladoc

• Fix(#16610): warn ignored Scaladoc on multiple enum cases #19555

TASTy format

• Add patch for undefined behavior with object $ #19705
• Fix(#19806): wrong tasty of scala module class reference #19827
• Used derived types to type arguments of dependent function type #19838

Tooling

• Java TASTy: use new threadsafe writer implementation #19690
• Remove -Yforce-inline-while-typing #19889
• Cleanup unnecessary language flag #19865
• Bugfix: Auto imports in worksheets in Scala 3 #19793
• Refine behavior of -Yno-experimental #19741

Transform

• Short-circuit isCheckable with classSymbol #19634
• Avoid eta-reduction of (..., f: T => R, ...) => f.apply(..) into f #19966
• Tweak parameter accessor scheme #19719

Typer

• Update phrasing for NotClassType explain error message #19635
• Fix java typer problems with inner class references and raw types #19747
• Approximate MatchTypes with lub of case bodies, if non-recursive #19761
• Revert broken changes with transparent inline #19922
• Delay hard argument comparisons #20007
• Fix #19607: Allow to instantiate wildcard type captures to TypeBounds. #19627
• Fix #19907: Skip soft unions in widenSingle of widenInferred #19995
• Fix untupling of functions in for comprehensions #19620

Contributors

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

According to git shortlog -sn --no-merges 3.4.1..3.42-RC1 these are:

    46	Nicolas Stucki
    33	Martin Odersky
    25	Dale Wijnand
    22	Hamza REMMAL
    18	Yichen Xu
    17	Jamie Thompson
    15	Szymon Rodziewicz
    11	EnzeXing
    11	i10416
     7	Paweł Marks
     6	Kacper Korban
     4	Dan13llljws
     4	Katarzyna Marek
     4	Matt Bovel
     4	Som Snytt
     4	noti0na1
     3	110416
     3	Eugene Flesselle
     3	Sébastien Doeraene
     3	dependabot[bot]
     2	Bersier
     2	Hamza Remmal
     2	Jakub Ciesluk
     2	João Costa
     2	Jędrzej Rochala
     2	Natsu Kagami
     2	Stephane Bersier
     2	Taro L. Saito
     2	aherlihy
     1	Aleksander Boruch-Gruszecki
     1	Aviv Keller
     1	Eugene Yokota
     1	Guillaume Martres
     1	Jan Chyb
     1	Lukas Rytz
     1	Mikołaj Fornal
     1	Olga Mazhara
     1	Ondřej Lhoták
     1	Robert Stoll
     1	Seth Tisue
     1	Valentin Schneeberger
     1	Yilin Wei
     1	willerf