While fixing bug 1755807 I started hand-waving that the not-helpful behavior of "go to definition" for IDL methods picking the C++ binding was pre-existing and would be potentially addressed by bug 1727789, but realistically bug 1727789 is going to be at least a month.

I'm addressing bug 1748959 as part of this, as changing us to use the "IDL" record instead of the "def" record still ended up going through the CGI define route which would then still pick the definition[1].

1: And which I'm not altering right now, although arguably it should be updated, but I'd like to add test coverage for any changes around that since it will no longer be a commonly used feature.

This is now landed and operational in mozilla-central and will take effect in other trees as they are re-indexed.

While I don't think this should result in any direct regressions, I do expect this working better to result in people realizing other rough edges in how searchfox perceives XPCOM implementations relative to the interfaces. In particular, people probably would want direct access to a singleton "Overridden By".