ffjson accepts invalid JSON on UnmarshalFast and Unmarshal

[echlebek]

The JSON specification states that objects keys must be strings. However, ffjson will accept object keys that are not strings. This can be seen in the attached test case. (Generated code not attached.)

foo.go

package ffjsontest

type Foo struct {
	Values map[uint64]string
}

foo_test.go

package ffjsontest

import (
	"encoding/json"
	"testing"

	"github.com/pquerna/ffjson/ffjson"
)

func TestFFJSONUnmarshal(t *testing.T) {
	data := []byte(`{"Values":{0:"hello",1:"world"}}`)
	foo := Foo{}
	if err := json.Unmarshal(data, &foo); err == nil {
		t.Error("json.Unmarshal: expected error")
	}

	if err := ffjson.Unmarshal(data, &foo); err == nil {
		t.Error("ffjson.Unmarshal: expected error")
	}

	if err := ffjson.UnmarshalFast(data, &foo); err == nil {
		t.Error("ffjson.UnmarshalFast: expected error")
	}
}

$ go test
--- FAIL: TestFFJSONUnmarshal (0.00s)
       	foo_test.go:18: ffjson.Unmarshal: expected error
       	foo_test.go:22: ffjson.UnmarshalFast: expected error
FAIL
exit status 1