Binding of the map routine internally now requires list elements to bind as Pair, which improves the error message.
(The alternate approach of inserting a CATCH into the map closure could in theory produce an even better message, but it appeared to slow things down more than the Pair binding approach.) Note that we cannot make the degenerate case of .invert the same as .antipairs, because .invert must expand list values into multiple antipairs. In any case, .antipairs is 5-10 times faster since it doesn't have to check for such expansion. Fix in baeabb4c4e8f5d223da8632130b4dfcd020d40ba Test in 63c1f009b910a5c87186b2201383682ad7a0f724
