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Release Notes

Dear Community,

On behalf of the Haxe Foundation, we are proud to announce the official release of the Haxe 4.0.0-rc.2! It is available along with the changelog at

We now support ES6 generation by using the -D js-es=6 flag! Please test this with your Haxe/JavaScript codebases and let us know about any problems you come across.

Other than that, we fixed a lot of bugs and improved the quality of our error messages a little.

See the changelog below for further details. Please report any issues here:

Thank you very much for your help!

Change Log

2019-03-22: 4.0.0-rc.2

New features:

  • all : added strictness settings for the null-safety checker, using loose checking by default (#7811)
  • js : added ES6 class generation with -D js-es=6 (#7806)

General improvements and optimizations:

  • all : inherit @:native for overriden methods (#7844)
  • all : standardized identifiers allowed in markup literals (#7558)
  • all : show typo suggestions when declaring override field (#7847)
  • all : improved parser error messages (#7912)
  • all : improved diagnostics of syntax errors (#7940)
  • all : improved positions of switch and case expressions (#7947)
  • all : allow parsing #if (a.b) (#8005)
  • eval : improved performance of various string operations (#7982)
  • eval : fixed many error positions
  • eval : greatly improved debugger interaction (#7839)
  • eval : properly support threads when debugging (#7991)
  • eval : improved handling of capture variables (#8017)
  • js : generate dot-access for "keyword" field names (#7645)
  • js : optimized run-time type checking against interfaces (#7834)
  • js : skip generation of interfaces when no run-time type checking needed (#7843)

Standard Library:

  • all : unified various Thread APIs in sys.thread (#7999)
  • all : moved typed arrays from js.html to js.lib (#7894)
  • all : added iterator() to haxe.DynamicAccess (#7892)
  • all : added keyValueIterator() to haxe.DynamicAccess (#7769)
  • eval : completed Thread API


  • all : fixed argument default value checking for externs (#7752)
  • all : fixed optional status of overloaded arguments with default values (#7794)
  • all : fixed DCE compilation server state issue (#7805)
  • all : fixed compilation server module dependency issue related to macros (#7448)
  • all : fixed call-site inlining on abstracts (#7886)
  • all : fixed Constructible not checking constraints properly (#6714)
  • all : fixed @:structInit not being compatible with final fields (#7182)
  • all : fixed capture variables being allowed in .match (#7921)
  • all : fixed infinite recursion on @:generic field access (#6430)
  • all : fixed -D no-deprecation-warnings for typedefs and enums
  • js : fixed bad stack handling on Map constraint checks (#7781)
  • js : fixed DCE issues related to haxe.CallStack (#7908)
  • cpp : fixed Socket flags not being preserved (#7989)
  • lua : fixed broken output when compiling through the compilation server (#7851)
  • lua : fixed StringTools.fastCodeAt with -D lua-vanilla (#7589)
  • lua : fixed @:expose for classes inside packages (#7849)

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For getting started with Haxe, take a look at our introduction, read through the Haxe Manual or look at these use cases for Haxe, including tutorials and popular libraries: