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Covariance and contravariance explanation is wrong #3272

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Merged
jakebailey merged 1 commit into from
Nov 12, 2024
Merged

Covariance and contravariance explanation is wrong #3272

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2 changes: 1 addition & 1 deletion packages/documentation/copy/en/handbook-v2/Type Manipulation/Generics.md
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Expand Up @@ -449,7 +449,7 @@ interface Consumer<T> {
consume: (arg: T) => void;
}
```
Then we can use a `Consumer<Animal>` where a `Consumer<Cat>` is expected, because any function that is capable of accepting a `Cat` must also be capable of accepting an `Animal`.
Then we can use a `Consumer<Animal>` where a `Consumer<Cat>` is expected, because any function that is capable of accepting an `Animal` must also be capable of accepting a `Cat`.
This relationship is called *contravariance*: the relationship from `Consumer<T>` to `Consumer<U>` is the same as the relationship from `U` to `T`.
Note the reversal of direction as compared to covariance! This is why contravariance "cancels itself out" but covariance doesn't.

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