Follow up on def vs val in #940

[ceedubs]

In #940 some implicit instances that seemed like they should be able to be vals were forced to be defs. It would be nice to follow up on that - to try to figure out why that was and whether we can do something about it.

cc @djspiewak

[djspiewak]

Here's a quick instance where this happens:

cats/core/src/main/scala/cats/data/OptionT.scala

Line 140 in 7cdd661

implicit def optionTTransLift: TransLift.Aux[OptionT, Functor] =

Haven't tried in a while, but when I first wrote this line, swapping it from a def to a val made the implicit it provides unresolvable (the tests will fail to compile, so it's easy to check).

[ceedubs]

@djspiewak yes, I saw the same behavior when I didn't believe you and tried to change it to a val :P

[djspiewak]

@ceedubs Doubter… ;-)

[ceedubs]

This is no longer relevant after #1621.