`route.ID()` returns conflicting IDs

[grobinson-grafana]

What did you do?

It is possible to write an Alertmanager configuration file where route.ID() returns conflicting IDs. For example, the configuration file:

receiver: test
routes:
- matchers:
    - foo=bar
  continue: true
  routes:
  - matchers:
    - bar=baz
- matchers:
    - foo=bar
  continue: true
  routes:
  - matchers:
    - bar=baz

gives the following Route IDs:

{}
{}/{foo="bar"}/0
{}/{foo="bar"}/{bar="baz"}/0
{}/{foo="bar"}/1
{}/{foo="bar"}/{bar="baz"}/0

What did you expect to see?

It should give these IDs instead:

{}
{}/{foo="bar"}/0
{}/{foo="bar"}/0/{bar="baz"}/0
{}/{foo="bar"}/1
{}/{foo="bar"}/1/{bar="baz"}/0