According to:

http://api.mongodb.org/cplusplus/2.2.0/classmongo_1_1_b_s_o_n_element.html#a692f3eecb505eae2181eb938b7680fbe

Double() (and like functions) should "throw a UserException if the element is not of the required type."

My code:

{{ BSONObj a_document = BSON("a_string"<<"A string");

try

{ a_document["a_string"].Double(); }

catch(mongo::UserException ue)

{ cout << ue.toString() << endl; }

}}
But it doesn't get caught. Instead it asserts:

{{Sun Dec 09 16:04:28 Assertion: 13111:wrong type for field (a_string) 2 != 1
Sun Dec 09 16:04:28 dev: lastError==0 won't report:wrong type for field (a_string) 2 != 1}}

My reading of bsonelement.h indicates it is throwing a MsgAssertionException – see line 472.

Is the documentation or my understanding incorrect?

Thanks!