v0.109.0

Likely to cause new Flow errors:

• Flow was previously not typechecking delete, but now does
• Object.defineProperty and similar methods now adhere more closely to the spec
• Allow defaults for properties that may not exist in React components

Notable bug fixes:

• $NonMaybeType<mixed> no longer includes null and undefined (Thanks @goodmind)

Misc:

• Deprecated $Supertype and $Subtype utilities are now removed entirely
• flow-upgrade should now use https over git (Thanks @lukeapage)
• Autocomplete now fires on spaces in JSX
• Better error messages when a value is used as a type

Performance:

• Reduced memory usage by using a more compact representation for code locations
• Types-first should no longer check direct dependents of files where the signature has not changed

Library Definitions

• Add a number of CSSOM interfaces + fix HTMLStyleElement.sheet type (Thanks @kof)
• Add AsyncIterator to node.js (Thanks @goodmind)
• Add undefined to prelude (Thanks @goodmind)
• Add String.prototype.matchAll (Thanks @goodmind)