Foo(X): Int | Null = null bar(x: Int | Null): Int

Question

Foo(X): Int | Null = null bar(x: Int | Null): Int

= x match {
case null => 0
case s => 42 + s

s.map(foo).map(bar) =? s.map(foo andThen bar)

—————————

1)
s: Int|Null = 2

s.map(foo) = null
null.map(bar) == 0

s.map(foo andThen bar) == 0

2) s: Int|Null = null
s.map(foo) == null
null.map(bar) == 0

s.map(foo andThen bar) == 0

—————————

implicit class Q(x: T|Null) {
def map[K](f: T => K): K|Null =
if (x == null) null else f(x)
}

null.map(f: T => K) == null