Panic if attempting to compare supposedly-disjoint maps with pointer-valued keys
Panic if attempting to compare supposedly-disjoint maps with pointer-valued keys

Recursive equality of maps depends on == (not recursive) equality of
keys; disjoint maps can never have keys which are ==, so we are almost
certainly not doing what the user actually wanted / expected.

google/CodeCity,google/CodeCity,google/CodeCity,NeilFraser/CodeCity,NeilFraser/CodeCity,google/CodeCity,NeilFraser/CodeCity,NeilFraser/CodeCity