FunctionLoweringPass didn't add much value over FileLoweringPass, but
had a hidden footgun (like ClassLoweringPass) in that if your lowering
pass invoked a visitor/transformer on the function body and you forgot
to override visitFunction to stop visiting nested functions,
runOnFilePostfix would work with the complexity of the squared number of
nesting levels. It looks like this was happening with K/N's
DataClassOperatorsLowering (I haven't measured though).
(cherry picked from commit 822410a647560826e8cce96921eae32f237cf335)
Alexander Udalov
297361f0c8