ESQL: Referncing children of nested fields doesn't always fail

Elasticsearch Version

8.16

Installed Plugins

No response

Java Version

bundled

OS Version

cloud

Problem Description

ESQL isn't always making an error when referring to a nested field.

Steps to Reproduce

Make an index with a mapping like:

"process": {
              "type": "nested",
              "properties": {
                "entity_id": {
                  "type": "text"
                },
                "name": {
                  "type": "keyword",
                  "ignore_above": 1024
                },
                "pid": {
                  "type": "long"
                }
              }
            },

Then write a query like FROM foo* | WHERE process.name = "bar". That fails like it should - we don't know what the process.name field is because we don't understand nested. But if you write

FROM foo*
| EVAL s = CASE(process.name RLIKE ".*adfadsfdaf", 1, 0)
| WHERE s == 1
| STATS COUNT(*) BY process.name

that doesn't fail. Or didn't in an example I'm looking at. Neither does this:

FROM foo* | STATS COUNT(*) BY process.name

Now this could have something to do with foo* matching an index with the nested mapping and one without - but I'm not sure.

Logs (if relevant)

No response

elastic / elasticsearch