Kotlin 1.0.0-RC: What's new.md

Kotlin 1.0.0 RC

To get rid of all the old code, this version requires recompilation of all dependencies.

NOTE: EAP users must recompile their code all the same, although the compiler won't demand this (IllegalAccessError is likely to be thrown at runtime)

• Language
  • new @delegate: use-site target for annotation (e.g. @delegate:Transient)
  • private top-level Kotlin classes should be compiled to package private java classes
  • unfinished multiline comment is an error
  • previously deprecated language constructs are now errors
  • type ckecking for use-site variance fixed
  • generic functions are compared for specificity through solving a constraint system
  • having multiple vararg parameters for one function is prohibited
  • super-calls to functions with default parameters are prohibited (pass all arguments explicitly)
  • implicit receiver behavior fixed
  • as-import removes original names if they were imported before
  • user code is not allowed in kotlin.** packages
  • type parameters of extension properties allowed to be indirectly used by the receiver type
  • members of private classes can-not be accessed from non-private inline functions
• Java interop
  • forEach from Kotlin's library is preferred to forEach from java.lang.Iterable
  • synthesized declarations (like JavaBeans properties and SAM-converted methods) are now resolved on par with members
  • support added for Java setters that return values
  • previously depreacted Java declarations removed from generated code
  • private setters allowed for lateinit properties
  • wildcards are not generated for redundant type projections (use List<@JvmWildcard Foo> instead of List<out Foo>)
  • @Nullable/@NotNull annotations from different standard Java packages recognized (javax.annotations, Guava, Android, etc)
• Standard Library
  • diagnostics for multiple conflicting Kotlin runtime versions in classpath
  • some functions have been made inline
  • many inline functions (most of them one-liners) can no longer be called from Java code. This will help us reduce the size of the runtime library in the future.
  • library code rearranged into more granular packages (no source changes should be required)
  • associate and associateBy are added to aid construction of maps associate and associateBy (instead of toMap/toMapBy)
• groupBy with key- and value-selector functions
• Map.getOrElse() and Map.getOrPut() now treat keys associated with null values as missing.
• Map.getOrImplicitDefault() has been made internal
• mutableListOf, mutableSetOf, mutableMapOf added to construct mutable collections. linkedListOf is deprecated
• toMutableList added instead of toArrayList. The latter is deprecated
• kotlin.system.exitProcess instead of System.exit
• File.deleteRecursively only returns false in case of incomplete deletion
• File.copyRecursively allows overwriting by specifying argument overwrite=true
• changed File.copyTo behavior to be like Files.copy from JDK8.
• more specific return type for File.inputStream, File.outputStream, String.byteInputStream.
• IO utility functions taking charset name as a string are deprecated, use ones with Charset parameter.
• File.useLines and Reader.readLines are introduced
• File.(buffered)reader/writer now return less specific InputStreamReader/OutputStreamWriter and use UTF-8 encoding by default
• Comparator- and comparison-related functions are moved to kotlin.comparisons package (not imported by default)
• new properties in MatchResult: groupValues and destructured — provided for easier handling of regular expression match results
• Lazy is now an interface open for implementation
• kotlin.system.measureTimeNano renamed to measureNanoTime.
• plusElement and minusElement functions as a synonyms for list + element and list - element.
• kotlin.test.assertFailsWith with Class<T> parameter is deprecated, use an overload with KClass<T>.
• toLinkedMap is deprecated.
• UTF_32 charset properties added to Chatsets
• Tools
• To enable Android Extensions, use: apply plugin: 'kotlin-android-extensions'
• IDE
  • Intention to replace iteration over map entries with a loop using a destructuring declaration
  • Inspection and quickfix to cleanup redundant visibility modifiers
  • Inspection to replace 'assert' calls checking that a variable is not null with !! or ?: error(...)
  • Show "Kotlin not configured" notification when opening a .kt file in the IDE if the Kotlin runtime is not configured for the corresponding module
  • Action to generate the toString() method
  • Support for implementing members by primary constructor parameters
  • Parameter info popup works for showing type parameters
  • Completion offers name variants based on unresolved identifiers in current file
  • Quickfix for adding missing branches to a when expression
  • Support for moving nested classes to the upper level or into another top-level class
  • @Suppress now works for IDE inspections