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doc --> dog (#3330)

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feek 2020-05-10 08:19:54 -07:00 committed by GitHub
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docs/annotating_code/templated_annotations.md
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@ -330,7 +330,7 @@ function takesDogList(Collection $dog_collection) : void {
}
```
That last call `addAnimal($doc_collection)` breaks the type of the collection – suddenly a collection of dogs becomes a collection of dogs _or_ cats. That is bad.
That last call `addAnimal($dog_collection)` breaks the type of the collection – suddenly a collection of dogs becomes a collection of dogs _or_ cats. That is bad.
To prevent this, Psalm emits an error when calling `addAnimal($dog_collection)` saying "addAnimal expects a `Collection<Animal>`, but `Collection<Dog>` was passed". If you haven't encountered this rule before it's probably confusing to you – any function that accepted an `Animal` would be happy to accept a subtype thereof. But as we see in the example above, doing so can lead to problems.