ALF11 — NameExpression::assignment Derivation for a Parameter Name

Subclause: 13.2.34 NameExpression

For a parameter name, nameExpressionAssignmentDerivation should only give the assignment as the assignment before the expression if there is one. Otherwise, it should create an effective assignment with the formal parameter as its source element, unless the parameter is an out parameter. If the parameter is a non-Alf element, then this will need to be wrapped in a new ExternalParameter syntax element.

Allow an assigned source to be an external reference

Agreed in principle. However, rather than introduce a new ExternalParameter class, a better solution would seem to be to make the source of an AssignedSource an ElementReference, rather than a SyntaxElement. This would reuse the general mechanism to allow a reference to be to either an internal or external element.