facebook/flow

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Adds static typing to JavaScript to improve developer productivity and code quality.

Stars: 22.3k
Forks: 1.9k
Open beginner issues: 0
Indexed issues: 510

Dominant language: Rust
License: MIT
Last GitHub push: Sep 15, 2026
Latest indexed: Sep 15, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: good first issue help wanted
PR merge metrics: No merged PRs in 30d

Open All

510 open issues indexed

Flow does not find files behind a symbolic link directory path Open

Windows support

facebook/flow#4015 · 14 comments · 29 reactions · 0 assignees · Indexed Sep 15, 2026
Type refinement breaks on simple, exact object types Open

Typing: refinements

facebook/flow#4027 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Higher Order Classes Open

facebook/flow#4031 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
version mismatch error disobeys --json Open

bug

facebook/flow#4038 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Disjoint unions with exact types - poor inference of typeof undefined check Open

Typing: object model Typing: refinements Typing: unions/intersections

facebook/flow#4048 · 5 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Is "declare" even necessary? What is it for anyway? Open

question

facebook/flow#4053 · 9 comments · 2 reactions · 0 assignees · Indexed Sep 15, 2026
Flow doesn't check type in switch when case is a variable Open

facebook/flow#4056 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Goofy `instanceof` refinement under a bounded polymorphic function Open

bug Typing: refinements

facebook/flow#4064 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Autocomplete results incomplete when including from library. Open

autocomplete

facebook/flow#4066 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Error using union types in interface Open

question Typing: interfaces Typing: property variance

facebook/flow#4084 · 3 comments · 1 reaction · 0 assignees · Indexed Sep 15, 2026
RegExp.prototype.exec returns `any` Open

Library definitions

facebook/flow#4099 · 0 comments · 4 reactions · 0 assignees · Indexed Sep 15, 2026
"Required module not found" for subdirectories of node modules. Open

facebook/flow#4133 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Autocomplete instance inherit properties cannot work with default type parameters Open

autocomplete

facebook/flow#4141 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Flow typechecking fail when importing via absolute path with react-native Open

facebook/flow#4186 · 13 comments · 12 reactions · 0 assignees · Indexed Sep 15, 2026
instanceof (and probably other) checks don't refine with direct boolean comparison Open

bug

facebook/flow#4192 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
`boolean` is incompatible with `true | false` Open

feature request

facebook/flow#4196 · 6 comments · 14 reactions · 0 assignees · Indexed Sep 15, 2026
`import type Foo...` is not semantically equivalent to `import type * as Foo...` Open

question

facebook/flow#4197 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
class declaration with overloaded methods and the mixed type cause return type to be any Open

facebook/flow#4198 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Flow doesn't see external modules, starting with 0.46 Open

facebook/flow#4200 · 4 comments · 5 reactions · 0 assignees · Indexed Sep 15, 2026
What is the best way to express an inner class? Open

facebook/flow#4204 · 13 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[Help] Function that returns a polymorphic instance of a Class Open

facebook/flow#4210 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Can't use first type parameter as type bound for second parameter Open

facebook/flow#4218 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Please consider using a different file extension. Open

discussion

facebook/flow#4233 · 5 comments · 28 reactions · 0 assignees · Indexed Sep 15, 2026
Renaming a file with flow errors, changing only its case, leaves errors behind associated with old file name Open

facebook/flow#4235 · 0 comments · 2 reactions · 0 assignees · Indexed Sep 15, 2026
Premature class `this` specialization Open

bug Typing: object model

facebook/flow#4240 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Internal error: unexpected rest parameter, expected an identifier pattern Open

bug

facebook/flow#4244 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Combining intersection with union problem Open

facebook/flow#4247 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Object types intersection within generics within object types Open

facebook/flow#4258 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Errors in the wrong places... ie, errors at type declarations, and top of stack... Open

error messages

facebook/flow#4261 · 0 comments · 1 reaction · 0 assignees · Indexed Sep 15, 2026
For an unknown index into a tuple, Flow neglects potential void types resulting from out of bounds access Open

Typing: tuple

facebook/flow#4264 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
(a | b) & c != (a & c) | (b & c) for objects Open

facebook/flow#4269 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Generic type capture violates constraints when using union type for possibly null/undefined function parameter Open

facebook/flow#4271 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[Question] Use external constant when defining flow literal type Open

facebook/flow#4279 · 12 comments · 6 reactions · 0 assignees · Indexed Sep 15, 2026
Unions of objects and their properties Open

facebook/flow#4299 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
import type doesn't show error from file with no flow pragma Open

facebook/flow#4311 · 0 comments · 1 reaction · 0 assignees · Indexed Sep 15, 2026
[libs] in .flowconfig to use globs? Open

feature request

facebook/flow#4323 · 4 comments · 14 reactions · 0 assignees · Indexed Sep 15, 2026
Flow can't distinguish shapes of union types when testing the shapes of properties within the subtypes Open

Typing: refinements Typing: unions/intersections

facebook/flow#4328 · 13 comments · 12 reactions · 0 assignees · Indexed Sep 15, 2026
Incorrect constructor detected when using a Function in the left side of `extends` Open

facebook/flow#4331 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Confuse behavior when comparing enum Open

facebook/flow#4347 · 0 comments · 1 reaction · 0 assignees · Indexed Sep 15, 2026
Flow does not refines type of class union as it does with types Open

bug Typing: refinements

facebook/flow#4353 · 1 comment · 2 reactions · 0 assignees · Indexed Sep 15, 2026
Classes treated as second class citizens Open

Typing: destructors

facebook/flow#4360 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Flow doesn't resolve file names without extensions Open

facebook/flow#4368 · 0 comments · 1 reaction · 0 assignees · Indexed Sep 15, 2026
Cannot find files with multiple extensions (e.g. fileName.decorator.js) Open

facebook/flow#4378 · 5 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Callback's polymorphic return type will make whole function's polymorphic return type nullable Open

facebook/flow#4389 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Provide a way to define tuple sucseccsion types Open

Accepting PRs feature request Has PR Typing: tuple

facebook/flow#4413 · 7 comments · 2 reactions · 0 assignees · Indexed Sep 15, 2026
Array length mismatch when destructuring is not an error? Open

bug Typing: tuple

facebook/flow#4444 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Per-method bound for T defined on class? Open

facebook/flow#4450 · 7 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
General Feedback Open

discussion

facebook/flow#4451 · 3 comments · 11 reactions · 0 assignees · Indexed Sep 15, 2026
Flow does not refine type parameter based on type being parametrized Open

Typing: refinements

facebook/flow#4455 · 6 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Proposal: Allow only Error instances to be thrown Open

feature request linter

facebook/flow#4476 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026

facebook/flow

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