New Features:

• Added support for string and number literal properties in declare class and interface

Library Definitions:

• Change the Record<K, T> utility type's key bound from K: string to K: PropertyKey, allowing number and symbol keys in addition to string
• Added some TS built-in types that were missing from Flow's core lib

Misc:

• When experimental.allow_variance_keywords is set to true, we support the keywords in / out / readonly along with +/- for variance

New Features:

• Support constructor type signatures (new (...) => Type) in interfaces and declare class

Misc:

• When allow_variance_keywords is set to true, Flow stops erroring for in / out / readonly

No significant changes.

Parser:

• The 5 enum body ESTree node types (EnumBooleanBody, EnumNumberBody, EnumStringBody, EnumSymbolBody, EnumBigIntBody) have been replaced with a single EnumBody node. Its members property is a flat array of per-type member nodes (EnumBooleanMember, EnumNumberMember, EnumStringMember, EnumBigIntMember, EnumDefaultedMember). The explicitType property is now a string ("boolean", "number", "string", "symbol", "bigint") or null (previously a boolean). hasUnknownMembers remains a boolean. Several enum validation errors are no longer reported by the parser and are instead reported by the type checker.

Library Definitions:

• Add type definition for RegExp.escape()

• Misc: Store exports index in saved state

Notable bug fixes:

• Support numeric literal object keys when importing/exporting object literals
• Allow type keywords like infer to appear as member names in qualified type access (e.g. type S = O.infer;).
• Allow type keywords (readonly, keyof, infer, etc.) as function type parameter names

Parser:

• It is now a parse error to have a ? optional modifier in various places this does not make sense, e.g. const x? = 1;

Misc:

• API change: flow check becomes an alias of flow status. You can use flow full-check to trigger a full foreground check of a Flow root.

• Fix in Meta-internal saved state logic

New Features:

• Support for using well-known symbols as property names in types - the form should be exactly Symbol.iterator.

Notable bug fixes:

• Report prop-missing errors for unbound module properties in explicit type args used with implicit instantiation (e.g. try-Flow)

Library Definitions:

• Updated core.js library definitions to accept readonly tuples in Map constructor

• Fix in saved state on projects including files outside the project root.

Misc:

• Add autofix for colon-style type parameter bounds to extends-style type parameter bounds