Scala 3.1 is backwards binary-compatible with Scala 3.0: libraries compiled with 3.0.x can be used from 3.1 without change.

Notable changes

New experimental feature: safer exceptions #11721
Emit efficient code for switch over strings #11937
Add reflect SourceFile.{getJPath,name,path} #13177
Support -Wconf and @nowarn #12857
Fix #9482: simplified Manifest synthesis #13142
Scaladoc: Integrate Scastie into Scaladoc #13258
Add reflect Unapply.apply #13298
Change @experimental spec #13305
Update the tasty inspector returned value #13316
Add Wildcard in reflection #13363
Add TypedOrTest as super type of Typed in reflection #13362

Stabilized API

scala.Selectable.WithoutPreciseParameterTypes #13315
Symbol member methods in reflection API #13314
scala.quoted.Type.valueOfTuple #13313
Quotes abort API #13312
Quotes.reflect.TermParamClause.isErased #13311

Other improvements

Language and compiler

Add CanEqual typeclass instances of Option, Either and Tuple for strictEquality #12419
Synthesise Mirror.Sum for nested hierarchies #11686
Added better explanation for tree, that cannot be typed #12717
Allowing local variables to be initialized with non-hot values in initialization checker #12867
Use StringConcatFactory for string concatenation on JDK 9+ #12929
Add explanation to "already defined" message #13090
Do not require @experimental on anonymous classes #13155
Make body of quotes inlinable #13188
REPL: display the compiler + Java version on startup #13193
Teach backend to emit iinc instructions #13214
Allow IntSetting's to be set with a colon #13267
Add CanEqual typeclass instance for Seq to match Nil case#13265
Simplify & clarify TASTy isVersionCompatible #13280
Allow semicolon between type match cases #13338
Allow experimental erased in experimental scopes #13394
Add TypeRepr.isTupleN to reflection API #13384
Allow experimental language imports in experimental scopes #13417
Allow -source 3.1 as a version #13617

Documentation

Update the docs, change sidebar url property to page/index #13004
Inkuire search engine UI improvements #13052
Generate flat documentation structure for API rather than putting everything in api directory #13130
Add heuristic to support Context Bounds #13172
Add snippet includes feature. Introduce new snippet UX/UI. #13217
Add version browsing for nightlies #13244
Fetch Inkuire at scaladoc build instead of documentation generation #13287

SemanticDB

Signature information #12885
Support new Scala3 modifiers #13239
Support synthetics: implicit params, context params, and implicit conversions #13288
Support overridden_symbols#13295

Other bug fixes

Fix parsing Java annotation values #11809
Fix #11318: Assertion failed when not adding prefix to extension method in method body #11882
Fix #10900: Avoid loop for F-bounds in checkCanEqual #12747
Fix regression in provablyDisjoint #12786
Do no widen constant type on selector type in inline matches #12902
Make def generated from givens not synthetic #12979
Fix non-determinism in -Ysafe-init external method trace: #12989
Exhaustivity warnings on nested case classes #13030
Fix constructors Java generic signatures #13047
Set TimeZone for version number #13051
Avoid auto-tupling in unapply unless a tuple is expected #13063
Handle overloaded members when generating Java varargs bridges #13066
Fix definition of enclosingExtensionMethod #13078
Fix syntax of extension methods #13079
Refine "can be handled by parent" condition when generting bridges #13092
Suppress "no outer defs" check for Java sources #13108
Fix MatchError in Scaladoc Scalajs script #13115
Escape illegal characters in scaladoc code blocks #13118
Run PatternMatcher earlier, in the group before ExplicitOuter #13124
Deskolemise patterns to suppress exhaustivity warnings #13137
Analyze end markers when looking ahead #13139
Fix #13131: escape java array in ClassTag #13156
Handle isDefinedInCurrentRun on no symbol #13157
call deleteOnExit() after creating temporary scripting compile directory #13171
Detect cyclic dependencies when loading modules #13178
Fix #12800: Clarify match type reduction error on empty scrutinee #13184
Fix intrinsic types documentation when there is no scala package on files to document path #13185
Remove color from scala.compiletime.codeOf #13186
Scaladoc fix 12813: type parameter in extension method is wrong #13191
Scaladoc fix #13148: Empty argument list is not shown in scaladoc in some cases #13192
Fix inherit doc warnings #13199
Fix bugs in RemoteLinksTests #13200
Scaladoc fix [#13194]: Ill formated codeblock #13202
Fix self types appearing as inherited in docs and docs leaking self type methods #13207
Fix #12178: cannot resolve ValueOf for type literal argument of opaque types #13210
Make Hole a proper Tree in Trees #13213
Weaken assertion for duplicate attachments #13224
Employ frozen_<:< instead of <:< within EtaExpansion extractor logic #13229
Fix docs of Reflect.Symbol.children #13232- Fix #13141 remove spurious coercion of * to a type identifier (was already a valid identifier) #13237
Don't export members that will be synthesized in case classes #13234
Fix a bug causing Scaladoc break when -release option is set. #13233
Fix running JARs from scala script #13246
Fix inspectTastyFilesInJar in TastyInspector #13254- Fix #10077: No kind inference for match types #13264
Fix executable jars #13263
Fix #9675: Type _ in MT patterns with correct kind #13262
Handle type alias in capturing wildcards #13260
Fix MatchError when printing match types from macros #13278
Decouple -print-tasty from compiler #13276
Emit unicode instead of octal literals #13273
Enter symbols under their target names after erasure #13269
Fix missing symbol occurrence of type params' type bounds for constructor #13284
Fix Context leak in deffered Annotation tree #13301
Reimplement constraint merging for correctness #13292
Restore unreachable warnings by converting literals #13290
Don't print parser output twice #13330
Allow prefix operators on the LHS of assignments #13328
Better utilizing GADT bounds for HKTs #13323
Fix displaying some signatures in scaladoc #13317
wildApprox: also approximate FunProto arguments #13361
Avoid crash by handling by-names under Typed #13354
Do not harmonize constant args if their type doesn't affect resType #13353
Fix #12973: scala 3 repl does not work with -cp argument, needs -repl as workaround #13343
Avoid cycle with F-bounded inner Java class #13341
Fix #13221: Set JavaStatic on Module fields of module classes in JSCodeGen. #13381
Fix unsound injectivity assumption when inferring GADT bounds #13380
Fix #13310: Parse empty Java compilation units as EmptyTree #13378
Print the type parameter bounds of higher kinded types #13372
Disallow inline secondary constructors #13370
Fix 12600: Handle ExprType during tab completion #13368- Fix transient in stdlib #13425
Enter implicit members in scope when inlining #13415
Fix problem when making package objects explicit during unpickling #13413
Remove leading infix test for if condition #13412
Don't crash when calling gc() on a committed TyperState #13408
Fix #10747: Raise type error on unreducible match type #12768
Set typer phase after InteractiveDriver.run #13530
Make batch files support installation path containing spaces #13577
Fix #13626: Wrong position of quote content #13627
Fix #10867: Normalize after applyIfParameterized in superType #13253
Generate static forwarders for object members in companion interface #13573

Contributors

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

According to git shortlog -sn --no-merges 3.0.2..3.1.0 these are:

    61  Martin Odersky
    51  tanishiking
    50  Nicolas Stucki
    39  Kacper Korban
    33  Andrzej Ratajczak
    22  Dale Wijnand
    22  Olivier Blanvillain
    21  Lukas Rytz
    17  Filip Zybała
    16  Yichen Xu
    15  Rikito Taniguchi
    14  Sébastien Doeraene
    12  Krzysztof Romanowski
    11  EnzeXing
     9  Guillaume Martres
     9  Jamie Thompson
     8  Tom Grigg
     6  Seth Tisue
     5  Alec Theriault
     4  Michał Pałka
     4  Phil
     3  Fengyun Liu
     3  Paweł Marks
     2  Vadim Chelyshov
     2  Dmitrii Naumenko
     2  Julien Richard-Foy
     2  Kevin Lee
     2  Liu Fengyun
     2  Stéphane Micheloud
     2  Tomasz Godzik
     2  Adrien Piquerez
     2  adampauls
     2  noti0na1
     1  Kai
     1  Jeremy Smith
     1  Som Snytt
     1  Anselm von Wangenheim
     1  Boris
     1  Arnout Engelen
     1  odersky
     1  Anatolii Kmetiuk
     1  PJ Fanning
     1  Matthieu Bovel
     1  Performant Data
     1  Mario Bucev
     1  Ruslan Shevchenko

Reporting Bugs

If you encounter a bug, please open an issue! 🙏

scala/scala3 3.1.0 on GitHub