此文字的类型是什么？

Question

From the mgo docs:

pipe := collection.Pipe([]bson.M{{"$match": bson.M{"name": "Otavio"}}})

Decomposing this statement, I see that the argument passed to collection.Pipe is of type []bson.M. Given that slices are initialized via []sometype{ ... } syntax, I conclude that the aforementioned slice contains exactly one item (so len == 1), and that this item is the {"$match": bson.M{"name": "Otavio"}} literal.

What is the type of this literal? Intuitively, I want to say it's a map[string]interface{}, but when I tried checking on the go playground, I'm unable to initialize a similar data structure: https://play.golang.org/p/7QKYaQPi6g

My question is therefore twofold:

1. What is the type of https://play.golang.org/p/7QKYaQPi6g (assuming I've made no mistake in my reasoning)
2. What am I doing wrong in x := {"foo": 1, "bar": 1}?

Answer 1

bson.M is just another name for map[string]interface{}. See its documentation. Its declared as,

type M map[string]interface{}

So, yes {"$match": bson.M{"name": "Otavio"} is of type bson.M