As part of the commit for SERVER-27991, which allows specifying a UUID instead of a collection name as the collection identifier for a find command, we check for both types when examining the collection identifier argument. Presently, if one fails to provide a find command with either a string or a BinData UUID, this results in the following error:

Failed to parse: find: 1.0. 'find' field must be of BSON type binData.

The order of the checkFieldType calls should be switched so the error that gets output when neither a UUID nor a collection name is specified says that BSON type "String" was expected.