> GuardMap(["hello", null], Text.Len(it)) // Result is i4?* since null maps to null.
GuardMap(["hello", null], Text.Len(it)) : i8?*
BndKind:Call, Type:i8?*, Bnd:(Call(∂.ForEach([map:1] [str(hello), str(<null>)]:s*, Call(∂.Guard([guard:2] Scope(1), Call(∂.Text.Len(Scope(2)):i8)):i8?)):i8?*))
Func sig: () to i8?*
Sequence: Seq<Opt<i8>>
 0) 5
 1) <null>
###
> WithMap(["hello", null], Text.Len(it)) // Result is i4* since null is not mapped.
WithMap(["hello", null], Text.Len(it)) : i8*
BndKind:Call, Type:i8*, Bnd:(Call(∂.ForEach([map:1] [str(hello), str(<null>)]:s*, Call(∂.Text.Len(Scope(1)):i8)):i8*))
Func sig: () to i8*
Sequence: Seq<i8>
 0) 5
 1) 0
###
