New Features:

• You may now write object literals with Flow Enum values as computed keys. This will result in a dictionary type, keyed by the Flow Enum type. Note that all possible Flow Enum representation types are valid object keys, so we just support all of them.
• You can usenumber typed keys (rather than just number literals) to create objects, these will be treated as dictionaries{[number]: T}

Notable bug fixes:

• Fixed soundness hole in subtyping of type guard functions (e.g.try-Flow)
• Fixed a bug that caused spurious errors when type guards were used in private methods (e.g.try-Flow)
• Flow will no longer invalidate refinements made before the loop for const-like variables within a loop (example)

IDE:

• For identifiers of array patterns bind to a require call, go-to-definition will jump to itself.

Library Definitions:

• The internal typeReact$FragmentType is removed from Flow's builtin global type definitions.