Fix type of onError. (#1339)
The function passed to Stream.handleError needs to accept either a
single argument of type `Object`, or an `Object` and a `StackTrace`.
Since this can't be expressed by the type system, it's checked at
runtime. As a result, the `check` function (as previously written)
would fail if ever instantiated with a type `T` that was narrower than
`Object`.
Prior to implementation of
https://github.com/dart-lang/language/issues/731 (improved inference
for fold etc.), this worked fine, because type inference always
supplied an argument type of `dynamic` or `Object` for the function
literals passed to `check`. However, with the inference improvement
enabled, it starts to infer other types, causing runtime failures.
The correct fix is to give the `event` argument of `onError` an
appropriate type.
1 file changed
