Likely to cause new Flow errors:

• Enforce that interfaces are supertypes of objects and classes. Also prevent objects from being a supertype of a class.
• Improve soundness ofthis typing by banning the unbinding of class methods (seehttps://medium.com/flow-type/sound-typing-for-this-in-flow-d62db2af969e).

New Features:

• You can require an exhaustive check of an enum in a switch statement that includes a default branch. This is enabled with the comment// flowlint-next-line require-explicit-enum-switch-cases:error.
• Autocomplete for object keys.
• Introduce aflow fix command to apply autofixes from the command line to a list of files.
• Enable a new check mode that uses significantly less RAM for large projects.

Notable bug fixes:

• Fix a bug that allowed nested anonymous functions inside a default export.
• Using the--ignore-version flag also prevents Flow from crashing when an invalid option is in the.flowconfig.

Library Definitions:

• Support theoptions parameter forrequire.resolve. (thanks@skeggse)
• Return a TypedArray instead ofvoid from TypedArraysort function. (thanks@goodmind)
• Return aDOMStringList instead of a string array fromIDBDatabase.objectStoreNames. (thanks@bnelo12)

Misc:

• Add--binary to theflow version command to see the path to the current binary.
• Prevent the LSP from exiting when an invalid option is in the.flowconfig.
• Autofix for amethod-unbinding error to replace the method with an arrow function.
• Autofix for aclass-object-subtyping error to replace the object type with an interface.