Error in parsing the input file

I have the following fragment in docker-compose.yaml:
```
extra_hosts:
- host.docker.internal:host-gateway
```
and parsing error is:
```
...
3: invalid IP address syntax
```

I have no idea how to debug such an error without looking into code.
I suppose other data type mismatch will report equally confusing messages.
Alternatively and more generic, reporting line number and even column helps narrow the offending directive.

Reproduce the parsing failure with the shown docker-compose.yaml fragment, then trace the input-parsing entry point to where the invalid IP address error is produced. Check how other data type mismatches are reported and whether parser location data is available. Done means the reported error identifies the offending line, and preferably column, without exposing an unhelpful internal message.

Written by the indexing model from the issue text.