DMD Symbol Reference Analysis Pass

[via Digitalmars-d]

Does DMD currently do any analysis of references to a symbol in a
given scope? If not where could this information be extracted (in
which visitor/callback) and in what structure should it, if so,
be stored?

Reason: After having read about Rust's data-flow (and in turn
escape) analysis I'm very curious about how difficult it would be
to add more clever type inference of, for instance, mutability, 
based on this analysis.

Two cases come to my mind:

A: Non-Templated Function: must be @safe (or perhaps @trusted)
pure and parameter must qualified as const (or in).
B: Templated Function: Usage of parameter in body must be
non-mutating; meaning no lhs of assignment op (=, +=, ...), and
calls to functions that take parameter as argument must be
transitively fulfill A and B.

I'm guessing

     Scope::insert(Dsymbol*s)
     {
         if (VarDeclaration *vd = s->isVarDeclaration())
         {
             // ..

is of interest. Is there another member function called everytime
a Dsymbol is referenced?

I'm guessing MODFlags plays a role here aswell.

I'm asking again because of the work recently done in DIP-25,
that may be related to this problem.