facebook/flow v0.332.0

on GitHub

Breaking Changes:

• no_flowlib option is removed. Use builtin_lib=flowlib (default) or builtin_lib=prelude instead.

Likely to cause new Flow errors:

• Render types no longer accept exact react element as arguments. See https://flow.org/en/docs/react/render-types/ for supported cases
• Flow will now always infer a react jsx element to be a render type if it's an element of a component-syntax component, or React.MixedElement otherwise. Legacy code that requires exact react element will see new errors.
• Add an option for rejecting dynamic imports in Haste modules.

New Features:

• Symbol() and Symbol.for() create a unique symbol when they initialize a const, so symbols can be used as property keys without explicit declarations.

Notable bug fixes:

• Bound error type normalization to prevent excessive memory use
• Release temporary signature-hash graphs after Flow merges.
• Using import typeof of a generic value without type arguments keeps its polymorphism instead of reporting missing-type-args, and renders accepts import typeof of a generic component.

Parser:

• Parse deferred imports: import defer * as ns from "m" and import.defer("m") now set the ESTree phase property to "defer".

IDE:

• Hover on members accessed through super shows the declaration
• Hover on destructuring keys shows the member declaration
• Hover on enum members shows the member declaration
• Hover on signature labels and indexer keys shows the parameter
• Hover on component attribute names shows the prop declaration
• Hover on import/export sources shows the module
• Hover on this-parameters shows the parameter
• Hover on indexed-access literals shows the member
• Hover on polymorphic JSX elements no longer exposes overly precise literal types when no annotation demands that precision
• Hover on a call to an overloaded function reports how many other signatures the function has
• Hover lists the signatures of an overloaded declaration instead of printing their intersection
• Component hovers no longer drop indexer rest props
• Align multiline union members in hover type declarations
• Render hover definition links in a compact Rust-style navigation row.
• Expand rest-prop aliases in top-level component hovers.

Library Definitions:

• React ref callbacks now have a stricter return type
• import.meta will no longer have url property and arbitrary unknown property. To add them back, you can do so through declaration merging (e.g. adding interface ImportMeta { url: string } to your global library definitions.
• ArrayLike and ArrayBuffer now follow TypeScript definitions
• Stricter typing for Array(length) and Array(items)