Notable Changes

Platform

• The standard library was upgraded to Scala 2.13.4, JDK 14 and 15 are now supported. (#10392)

Syntax

• The @infix annotation was replaced by an infix modifier, the @mixin annotation was replaced by transparent (#10458)
• The @alpha annotation was renamed to @targetName and can now be used to define overloads that would normally result in a double definition error (#10149)
• Drop extension_ prefix for extension methods (#10128)
• The Eql typeclass has been renamed CanEqual (#10449)

Reflection

Breaking changes

• QuoteContext has been renamed Quotes (#10432)
• Instead of importing qctx.tasty._, import quotes.reflect._ (#10442)
  • In general, scala.quoted.qctx was replaced with scala.quoted.quotes
• rootPosition is now Position.ofMacroExpansion (#10467)
• expr.unseal is now Term.of(expr)
• term.seal.cast[T] is now term.asExprOf[T]
• term.seal is now term.asExpr
• (tpe: Type[T]).unseal.tpe was replaced with TypeRepr.of[T]
• (tpe: Type[T]).unseal was replaced with TypeTree.of[T]
• (tpe: Type[T]).show was replaced with Type.show[T]
• scala.quoted.Type does not need to be named (implicitly only)
• (typeRepr: TypeRepr).seal is now (typeRepr: TypeRepr).asType
• Owners are now explicit in the reflection API (#10406)
• compiletime.code has been replaced with compiletime.codeOf (#10313)
• The syntax for type variables in quoted patterns has changed (#10125)
• Added quotes.reflect.Flags.{Opaque, Open}
• Added constructors for quotes.reflect.{TypeBoundsTree, WildcardTypeTree}
• Renamed quotes.reflect.{GivenMatch => SummonFrom}
• Renamed quotes.reflect.{Projection => TypeProjection}
• Changed constructor and extractor of quotes.reflect.Lambda
• Removed quotes.reflect.Context and replaced with explicit Symbol owners
  • In methods of TreeMap, TreeAccumulator and TreeTraverser
  • In ValDef.let formerly let
  • In Lambda.apply
  • In etaExpand
  • Added Tree.changeOwner and Symbol.spliceOwner
• Removed scala.tasty.Reflection (now it is inside Quotes)
• Reflection API uses TypeTests instead of ClassTags

Additions

• new API: TypeTest for safe type tests at runtime (#7555)

Scala.js

• Upgrade to Scala.js 1.3.1 (#10423)
• Implement the -scalajs-mapSourceURI option (#10439)
• Implement JS exports (#10164)
• Scala.js is now 100% supported

Scala3doc

• Numerous improvements over many PRs, Scala3doc is still not the default documentation tool (this requires setting useScala3doc := true), but it is now used to generate the https://dotty.epfl.ch/ website.
• For more information on Scala3doc see https://contributors.scala-lang.org/t/scala3doc-doctool-for-scala-3/4477