List comprehensions: variable is expected to have type [any()] but it has type none()

[erszcz]

I'm extracting this from #428 as as separate issue to track debugging effort.

ebin/gradualizer_lib.beam: The variable on line 170 at column 60 is expected to have type [any()] but it has type none()
ebin/typechecker.beam: The variable on line 737 at column 24 is expected to have type [any()] but it has type none()
ebin/typelib.beam: The variable on line 159 at column 71 is expected to have type [any()] but it has type none()
ebin/typelib.beam: The variable on line 189 at column 57 is expected to have type [any()] but it has type none()

A series of list comprehension related errors, stemming from the fact that vars in generators are assumed to be of type none().

git bisect shows something interesting:

$ git bisect bad
af24221ea3de423f12c2163490daf6dee3ee33f5 is the first bad commit
commit af24221ea3de423f12c2163490daf6dee3ee33f5
Author: Radek Szymczyszyn <[email protected]>
Date:   Thu Sep 30 00:14:20 2021 +0200

    Increase union_size_limit to 50

    When working on https://github.com/erszcz/tapl-erlang I ran into a type definition with >20 variants.
    It might make sense to make union_size_limit a runtime option, not a hardcoded value.

 src/typechecker.erl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

So it seems this only worked because of the any() approximation for big union types.