Record Flow type improvements #1870
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This allows for better type inference of the resulting RecordFactory. Fixes immutable-js#1722
mwiencek
commented
Jul 31, 2021
Comment on lines
154
to
157
| setName(name: string): this & TPerson { | ||
| // $FlowIssue[incompatible-return] | ||
| return this.set('name', name); | ||
| } |
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With the new changes, Flow doesn't like the this & TPerson return type one bit:
Error ┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈ type-definitions/flow-tests/record.js:155:12
Cannot return this.set(...) because: [incompatible-return]
• Either RecordInstance [1] is incompatible with this [2].
• Or TPerson [3] is incompatible with this [2].
type-definitions/flow-tests/record.js
[3] 147│ const PersonRecord = Record<TPerson>(defaultValues);
:
152│ }
153│
[2] 154│ setName(name: string): this & TPerson {
155│ return this.set('name', name);
156│ }
157│ }
158│
type-definitions/immutable.js.flow
[1] 1659│ set<K: $Keys<T>>(key: K, value: $ElementType<T, K>): this & $ReadOnly<T>;
Found 1 error
mwiencek
commented
Jul 31, 2021
| @@ -170,23 +169,6 @@ person.get('unknown'); | |||
| // $FlowExpectedError[prop-missing] | |||
| person.set('unknown', 'Thales'); | |||
|
|
|||
| // Note: not <TPerson> | |||
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I'm not sure what the use case here is (and PersonRecord is no longer parameterized anyway) so I removed the test altogether. If someone can explain the use case I can perhaps update it instead. :)
Edit: To be clear, the test right above this one is now class Person extends PersonRecord, so it's "without types" (though that isn't really possible anymore) now, and the .get('unknown'); there errors, which I think is correct, but which contradicts this test (at "Note: no error").
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Fixes #1722
I moved the
Valuestype parameter toRecord<Values>, so callingRecord(foo)can inferValuesfromfooand now returnsRecordFactory<Values>.This is a breaking change, though I believe it provides much better type checking for typical uses (and fixes at least one TODO). Unfortunately, this PR introduces issues when calling
RecordInstancemethods from a subclass (which I'm not sure how to fix), but that probably isn't super common, so the tradeoff might be worth it.