Still need import for `liftA2`

[kquick]

When compiling brick master with https://github.com/jtdaugherty/brick/commit/aeeee31e49de3e8a10955dd82354397d39243b29#diff-7fcd880a6e5d374a64e039c31c6f5831718ba254e6897611c168a2e860c6fb83R20 present, I get undefined errors for liftA2 with GHC 8.10 through GHC 9.4 (and possibly earlier versions) unless I change this check to #if !(MIN_VERSION_base(4,18,0)). I know this changed from a function to a class method in 4.10, but I'm not sure what warnings you were getting that let to this change, so I'm not sure of the proper fix needed here.

[jtdaugherty]

Hey, thanks for reporting this. I was getting a redundant import warning on newer GHCs (9.6? I forget precisely which). So I looked and found that this seems to have become redundant at the time that the type class change in 4.10, which is why I added the conditional import. But if you are seeing errors, then the import should be enabled but may just be wrong; do you know whether there is an additional state we need to allow for? E.g.,

• At some point liftA2 needed to be imported from somewhere else than Control.Applicative
• Then it was importable there, but still a function
• Then in 4.10 it became a type class method, rendering the import redundant