Access and mutation of routes' scope attribute

[Bertrand Petit]

	I'm in the process of upgrading a set of bird instances from v1 to v2.
The running configurations of these nodes were written circa ten years ago,
for a network that since has shrunk quite a lot, nethertheless I would like to
change them as little as possible. During preparation work I've hit a snag:
most of these configurations use routes scope as one of the filtering
criterions but bird v2 experience some grammatical difficulties when parsing
them.

	The user manual states that one can access and mutate a route scope
through the "scope" symbol (section 5.5). Nonetheless, the configuration file
parser rejects the following two functions---these are fictious functions
written to concisely replicate the problem, they are accompanied by the error
message produced by "bird -c <file> -p".


function ScopeAccess () -> bool
{
  return scope = SCOPE_HOST;
}
bird: 2025-11-26 10:30:02.631 [0001] <FATAL> scope-access.conf:3:10 syntax error, unexpected SCOPE


function ScopeSet () -> bool
{
  scope = SCOPE_HOST;
  return true;
}
bird: 2025-11-26 10:31:25.081 [0001] <FATAL> scope-set.conf:3:3 syntax error, unexpected SCOPE


	I had a quick look into "config.Y". I can't predend I fully understand
how the grammar is constructed due to a cursory glance, however I suppose the
constructions shown above are covered by the "term: ... static_attr ..." and
"cmd: ... symbol_known '=' term ';'" productions.

	When using the manual and these productions as supporting material I
think the two functions shown above are legit. Am I correct?

	Then I looked at "test.conf" where I found a construction involving
"scope" used not as an attribute but as a type, a declaration that is not part
of the documentation: "enum scope ev2 = SCOPE_UNIVERSE;". This construction,
accepted by the parser, is contradicting the user manual. Quoting it, section
5.2: "Enumeration types are fixed sets of possibilities. You can't define your
own variables of such type, but some route attributes are of enumeration
type."

	With regard to this undocumented declarative form, at this stage, I'm
wondering if a grammatical ambiguity could exist between "scope" the type and
"scope" the attribute?

-- 
%!PS -- Bertrand Petit
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