Types and filter method

[pulsar estuary]

you need to write a type predicate function for that

!hb type predicates

[lapis cloud]

Handbook / Narrowing

Using type predicates

[pulsar estuary]

the basic idea is that in most cases, .filter just removes some elements from an array
but the kind of elements stays the same
so .filter does not change the type, what goes in goes out

you need to change that