Context

The documentation for the bson package states the following:

uint, uint32, and uint64 marshal to a BSON int32 if the value is between math.MinInt32 and math.MaxInt32, inclusive, and BSON int64 otherwise.

The logic for this, added in GODRIVER-1358, is contradictory. The default case for the "min int" condition in the UintCodec is false / nil, which means that an type >= 32-bits will be considered int64. This can also be effected by EncodeContext.MinSize. 

package main

import (
	"fmt"

	"go.mongodb.org/mongo-driver/bson"
)

func main() {
	type foo struct {
		Bar uint32
	}

	m, err := bson.MarshalExtJSON(foo{2}, true, false)
	if err != nil {
		panic(err)
	}

	fmt.Println(string(m))
}

Definition of done

The documentation should be updated to the following:

When encoding with EncodeContext.MinSize set to true, uint, uint32, and uint64 will marshal to a BSON int32 if the value falls within the inclusive range of math.MinInt32 to math.MaxInt32. Otherwise, they will marshal to a BSON int64.

Pitfalls

What should the implementer watch out for? What are the risks?