• Fix a bug that causes fixed libdef-override error to stick around after an incremental recheck.

Likely to cause new Flow errors:

• Support for $PropertyType and $ElementType has been removed. Now referencing these types will just resolve to a global type if you have your own definition for them, and result in a cannot-resolve-name error otherwise. These types have been replaced by index access types for a long time. You can migrate to index access types by enabling use-indexed-access-type from https://www.npmjs.com/package/eslint-plugin-fb-flow and running the quickfixes. If you are unable to migrate, you can add the following to your global libdefs:

type $PropertyType<T, K> = T[K];
type $ElementType<T, K> = T[K];

• Now given the subtyping check component()<: component(ref?: ref_prop), Flow will ensure that ref_prop is a subtype of void instead of a subtype of React.RefSetter<void>.
• React$ComponentType, which was previously given [internal-type] error on every usage, is now removed.
• React.ComponentType<Props> is now only an alias of component(...Props), instead of some special cased types. This comes with stricter checks and conversions, such as making Props readonly, erroring on the presence the ref prop instead of silently ignoring them, and ensures that Props is a subtype of {...}. In addition, the React$AbstractComponent type is removed.

Notable bug fixes:

• fixed a subtle unsoundness in the inference of computed-property dictionary object creation (e.g. try-Flow)

Library Definitions:

• React.lazy and React.memo is now generic over the presence or absence of ref prop.

• Make @flowtyped resolution support work on Windows.

Notable bug fixes:

• We fixed a bug that caused suppressions to not apply for libdef-override errors.
• We fixed a bug that caused libdef-override errors not being raised even if it's turned on.

Notable bug fixes:

• Make libdef-override=off in [lints] section actually turn off all libdef-override errors.

Likely to cause new Flow errors:

• Overriding already defined names and modules in library definitions will now error with code [libdef-override]. The error cannot be suppressed without specific error code like $FlowFixMe[libdef-override]. It can be turned off by turning off the libdef-override lint.

New Features:

• The Number static methods Number.isFinite, Number.isInteger, Number.isNaN, and Number.isSafeInteger now apply a refinement that their input is a number. Note that the top level isNaN and isFinite functions (not off of Number) do not apply the same refinement as they first coerce their input to number.

Notable bug fixes:

• Fix a potential crash in libdef files with illegal import export. Thanks @techieshark for the repro.

Likely to cause new Flow errors:

• Signature verification errors will now show up for libdef files

New Features:

• Declaration merging for declare namespace is now supported in toplevel library definitions.

Notable bug fixes:

• In component type annotation, the ref prop can now have any type.

Library Definitions:

• Since the last version, most of the bundled libdefs will no longer be maintained and shipped with Flow. Going forward, they should be downloaded from flow-typed. Starting from this version, we will also no longer ship a set of precise typing definition for jsx intrinsics. To maintain the same behavior as before, you should have a flow-typed.config.json in the root of your project with the following content:

{
  "env": ["node", "dom", "bom", "intl", "cssom", "indexeddb", "serviceworkers", "webassembly", "jsx"]
}

Likely to cause new Flow errors:

• Signature verification errors will now show up for libdef files

New Features:

• Declaration merging for declare namespace is now supported in toplevel library definitions.

Notable bug fixes:

• In component type annotation, the ref prop can now have any type.

Library Definitions:

• Since the last version, most of the bundled libdefs will no longer be maintained and shipped with Flow. Going forward, they should be downloaded from flow-typed. Starting from this version, we will also no longer ship a set of precise typing definition for jsx intrinsics. To maintain the same behavior as before, you should have a flow-typed.config.json in the root of your project with the following content:

{
  "env": ["node", "dom", "bom", "intl", "cssom", "indexeddb", "serviceworkers", "webassembly", "jsx"]
}

Likely to cause new Flow errors:

• Referencing React$Component directly will now be an error.
• Use of React$ComponentType, React$Context and React$RefSetter will now trigger internal-type errors.

New Features:

• Added types for JSX intrinsics, which will cause new errors and show autocomplete for DOM intrinsics like div

Notable bug fixes:

• Replace incorrect definition for ClientRect and ClientRectList with aliases to DOMRect and DOMRectList
  This fixes the type definitions for the DOM APIs in Flow, but replacing an nonexistent globals ClientRect and ClientRectList types with just an alias to DOMRect and DOMRectList.
• fixed a bug that caused spurious errors on rest array assignments (e.g. try-Flow).
• When a library definition file has changed, Flow will no longer just stop the server. Instead, Flow will properly recheck everything, even under lazy mode.
• We now allow something of type React.ComponentType<{}> to be a subtype of component()

IDE:

• Component syntax components will now show up in document symbols

Library Definitions:

• Most of the bundled libdefs will no longer be maintained and shipped with Flow. Going forward, they should be downloaded from flow-typed. To maintain the same behavior as before, you should have a flow-typed.config.json in the root of your project with the following content:

{
  "env": ["node", "dom", "bom", "intl", "cssom", "indexeddb", "serviceworkers", "webassembly"]
}

Notable bug fixes:

• Fixed a bug that causes incorrect updates to our index that tracks usage of exports, which leads to incorrect autoimport-ranked-by-usage results.