The following two queries should be equivalent:

coll.find({a: {$in: [/abc/]}})
coll.find({a: {$in: [{$regex: /abc/}]}})

However, in 2.6.3 the former succeeds and the latter fails with "Can't canonicalize query: BadValue cannot nest $ under $in". We should support both forms of this query.

Original Description

Per this documentation, I assume that querying with the $in operator upon a list of regular expressions using either form of regular expression syntax, /^pattern/ or {$regex: "^pattern"}, is equivalent. However, the latter $regex operator syntax doesn't work.

v2.4.10 returns no documents, but v2.6.3 returns the 17287 error.

v2.7 nightly (mongodb-osx-x86_64-2b55561913f26870b0d4b1c8ec180139819eeba6-2014-07-16) also returns the 17287 error.