Revert "Ignore constants discovered in passing"

[zzak]

There was a regression due to d96a7a7.
I have reverted in f0646a3.

Need to test if this breaks #209, but tests still pass after revert.

Originally submitted in rails/rails#14150

[drbrain]

I don't see an easy way of determining how to keep the behavior from #209 without avoiding the breakage so I am punting this to Future.