Add validation error when a variable is not found in current block

[tpluscode]

With Class "http://localhost:5678/api#Installation" {
    Expect Operation "http://localhost:5678/api#InstallOperation" {
        Invoke {
            Expect Status 201
            Expect Header Location [entrypoint]

            Follow [entry]
        }
    }
}

In the snippet above the variable entry used does not match the entrypoint being "declared". It should be validated and an error shown guarding against such errors

[tpluscode]

@mchlrch instead of using a validator, is it possible to declaratively construct language so that it's only possible to reference variables within a block and no other variables are suggested?

[mchlrch]

For this case, it's best to adjust the scoping. The linker as well as proposals (code-assist) respect the scoping, so only elements in scope can be referenced.

I did this in the mapping-dsl as well, to scope the columns of a table that are eligible for the mapping

Implementation:
https://github.com/zazuko/rdf-mapping-dsl/blob/master/com.zazuko.rdfmapping.dsl.parent/com.zazuko.rdfmapping.dsl/src/com/zazuko/rdfmapping/dsl/scoping/RdfMappingScopeProvider.xtend