Local equations

abstract production id
lhs::Expr ::= n::String
{
  local refs :: [Decorated Dcl] =
    lookupName(n, lhs.env);
}

The preferred form of local declarations is shown above, as one production statement.

Production attributes (local visible to all aspects, not just the current production body) can be declared in the same way, except using production instead of local.

The old form of local declaration is two-part. First, the local is declared:

local attribute <name> :: <type>;

The name of the attribute and its type (following the has-type symbol ::) is similar to the name/type specifications in production signatures. This attribute can be referenced inside the production body. The separate definition of its value has the form

<name> = <expression>;

If the local attribute is a higher order attribute (its type is a nonterminal), then inherited attributes can be set on it just like they are set for the nonterminal children on the right-hand side of the production.

{
  local chain :: IOChain = print("hello, world");
  chain.inputIOToken = ioin;
}

Sometimes, one wishes to define a local or production attribute with a nonterminal type, that should not be a higher-order attribute. For instance, a local may portion of a larger tree being constructed, that is not directly supplied with inherited attributes. These locals can be marked as nondecorated:

{
  nondecorated local foo :: Expr = addOp(intLit(42), varExpr("x"));
  nondecorated production bar :: Expr = mulOp(foo, varExpr("x"));
}

The syntax nondecorated foo :: Expr = ...; is also available as shorthand for nondecorated local foo :: Expr = ...;.

Uses of a nondecorated local will have the undecorated nonterminal type, rather than the Decorated type for locals and children. Inherited equations and tree sharing are forbidden for nondecorated locals.

Currently, production attributes can be collections, but the legacy syntax must be used.

{
  production attribute contribs :: [Stmt] with ++;
  contribs := [];
}