meta/flow v0.340.0

on GitHub

Likely to cause new Flow errors:

• Class component configs are computed with React.ReactManagedAttributes
• Errors on keys read from keyof over an object with an indexer are now reported at the use of the key instead of at the indexer
• Arguments of Object static method calls that Flow doesn't type specially now get contextual types from the method's signature, like other method calls.
• use() calls in functions that Flow can't place in a component or hook now get the react-rule-hook-conditional error code instead of react-rule-hook.
• JSX intrinsics are typed by React.JSX.IntrinsicElements instead of $JSXIntrinsics, which Flow no longer reads. experimental.jsx_intrinsic_elements only accepts true.
• Class component configs always merge default props with React.ReactManagedAttributes. experimental.react_managed_attributes only accepts true.

New Features:

• Support fractional and other finite numeric property keys in Flow, using JavaScript property-name stringification.

Notable bug fixes:

• != null and truthiness refinements remove null and undefined from unions with optional or nested maybe members also when the union is optimized
• Truthiness and falsiness refinements filter intersection members represented by chains of type variables
• Methods of an interface with a construct signature, such as Number.isFinite and Date.parse, can be read without their receiver, like class statics.
• Reading prototype from a function or a callable object that doesn't declare it gives any, as declared by the builtin Function, instead of a prop-missing error
• Preserve nominal and intrinsic render types in match pattern bindings.
• flow-node no longer drops script arguments that equal a Node option passed before the script path.
• flow-upgrade adds the nameFunctionTypeParams and nameIndexerKeys codemods, and removeExplicitlyExactObjectTypeSyntax also removes ambiguous-object-type lint comments.

Parser:

• Parse TypeScript's definite assignment assertions on class fields, value!: T, and variables, let x!: T
• Fixed parse time that doubled with each level of nested conditional expressions with parenthesized consequents
• PropertyDescriptor and PropertyDescriptorMap are now interfaces, as in TypeScript
• Object is now declared as interface Object + interface ObjectConstructor, as in TypeScript
• Function is now declared as interface Function + interface FunctionConstructor, with CallableFunction and NewableFunction, as in TypeScript