Could `Sequential` satisfy `SearchableList` ?

I was experimenting with the in operator and "Hello" in "Hello world" lead me to try

print([1,2] in [0,1,2,3]);

which gave a warning “Tests containment with disjoint element types: ‘Integer[2]’ and ‘Integer’ are disjoint” and printed out false.

So after investigating, I found that SearchableList is involved in the substring search and wondered why Sequential couldn’t also support the same behaviour:

Encouraged by @jvasileff I reposted my question here.

[jvasileff]

Would it make sense for all Sequentials to be Categorys of both their elements and their sublists?

One reason not to is that “their elements and their sublists” aren’t necessarily disjoint. There would be two occurrences of [1, 2] in [1, 2, [1, 2]], which seems confusing.

[gavinking]

I don’t see any particularly strong reason why Sequential couldn’t inherit SearchableList<Anything>.

OTOH, I rarely use these operations, except on Strings, and they are actually somewhat heavy to implement.