the semantic analyser contains code that turns the AST into a non-tree directed acyclic graph.

if you have a function defined:

  void func (bool arg = true);

and later:

  void func2 () {
    func ();
  }

then the semantic analyser turns that into:

  void func2 () {
    func (true);
  }

but it does so without copying the "true".  the "true" here is actually the "true" from the function declaration (including sharing its source_reference).

more to the point, if you set the ccodenode while visiting the first true, then when you arrive at the second true you will find that it has already been set.

this is pretty harmless, but it means the AST is not really a tree anymore.  it may also confuse code generators (because of the ccodenode thing).