v0.24.0

New features:

• Many common errors now have more contextual error messages. Check out the test file changes to see what this looks like!
• If a <PROJECT_ROOT>/flow-typed/ directory exists, Flow will now assume it is a [libs] directory by default to help reduce the amount of out-of-the-box configuration that is necessary. (Thanks @splodingsocks!)
• Support for specifying a default on a type parameter declaration. For example: type Iterator<Yield, Return=void, Next=void> = ....
  • NOTE: The pull request to add syntax support for this is pending, so it may be necessary to wait on that to ship before using this feature

Notable bug fixes:

• Fixed the flow coverage command.
• Fixed crashes when running type-at-pos and dump-types over destructuring.
• Fixed a refinement bug when evaluating a method call on a refined variable in some cases.
• Fixed an issue where some system commands could throw if Flow attempts to read a directory that it doesn't have permission to read.
• Fixed a bug where the inferred return type of some functions that might return void could end up as exactly void (rather than a union of the possible return types).
• Fixed a bug where the server would crash if a .json file is deleted after a server was already running.
• Type applications that don't have the right number of type parameters (i.e. Map<number>) now emit a more clear error.
• Lots of dom/bom improvements sent in from contributors! (big thanks to @marudor for lots of these!)

Misc:

• Better locations for logical operator errors
• Better error message sorting:
  • Sorts errors in .json files by name coalesced with .js files
  • Sorts all internal errors before parse errors before type/inference errors
  • Sorts lib file errors before source file errors
• Perf improvements for some comparisons of polymorphic types