facebook/flow v0.327.0

on GitHub

New Features:

• In an object type, a bracketed key written as a string or number literal, or as the name of a value, is now a computed key naming a single property rather than an index signature, so several such keys can coexist. A key written as a type-only name is unchanged, and the labeled form [label: K] keeps index-signature semantics. Breaking: a key headed by a value binding is read as a computed key. Thus a class or enum key such as {[C]: V} is now an error, and a qualified type exposed through a class/namespace merge, as in {[C.K]: V}, must use the labeled form {[key: C.K]: V} to remain an index signature.
• In an interface or a declare class body, a bracketed key written as a string or number literal, or as the name of a value, is now a computed key naming a single property rather than an index signature, so several such keys can coexist, and static puts the property on the static side. A key written as a type-only name is unchanged, and the labeled form [label: K] keeps index-signature semantics. Breaking: a key headed by a value binding is read as a computed key, so a class or enum key such as interface I {[C]: V} is now an error and must use [key: C] to remain an index signature.
• A computed method key [expr](): T that resolves to a single literal string or safe-integer number is now accepted in interface, declare class, and object type bodies (previously a parse error outside .d.ts files) and reads as a named method.
• A bracketed access on an array with a string-literal key (for example arr['map'] or arr[Symbol.iterator]) now reads the corresponding named member instead of erroring that the key is not an array index, and a string key holding a safe integer (arr['0']) indexes the array like the equivalent numeric key.

Notable bug fixes:

• keyof any now evaluates to any as expected. Spurious errors related to the bug will no longer fire.
• Fix a server crash ("thread 'flow-tokio-runtime' has overflowed its stack") when rechecking a file with an attached LSP client

Parser:

• Parse component and hook type annotations as the declaration of declare export default

Library Definitions:

• Add ES2026 Map methods