I think you might be asking for a type :)

Not really. This is a syntactic error, not a type error.

To expand, this is the equivalent of something like {"a": 1, "b":}. The type checker in something like Typescript wouldn't ever come into play, because it's not legal syntax to begin with.

The parent was asking for the correct form, the syntax of EDN is necessary but not sufficient to specify this. A type (or a schema) is needed. Even if documented manually ad-hoc, that is better than nothing and would stop people needed to search the internet for examples.

It should be:

    {:deps
     {ring/ring-devel {:mvn/version "1.9.6"}
      ring/ring-core {:mvn/version "1.9.6"}}}

There was one too many map.