Aaron Hill 3540f9396a
Add disambiugator to ExpnData
Due to macro expansion, its possible to end up with two distinct
`ExpnId`s that have the same `ExpnData` contents. This violates the
contract of `HashStable`, since two unequal `ExpnId`s will end up with
equal `Fingerprint`s.

This commit adds a `disambiguator` field to `ExpnData`, which is used to
force two otherwise-equivalent `ExpnData`s to be distinct.
2021-01-23 15:41:17 -05:00
..
2021-01-23 15:41:17 -05:00