[pulse] also visit values involved in array accesses

Summary:
There was a bug where we forgot to mark these values as reachable. In
particular we would forget their arithmetic value as a result.

For example, now we remember that the array access is at an index equal
to 5 in the summary of this function:

```
foo(int a[]) {
  a[5] = 42;
}
```

Reviewed By: skcho

Differential Revision: D25430468

fbshipit-source-id: 4acf09842

infer/src/pulse/PulseBaseDomain.ml

@@ -245,11 +245,23 @@ end = struct
     let finish visited_accum = Continue visited_accum in
     Container.fold_until edges ~fold:Memory.Edges.fold ~finish ~init:visited_accum
       ~f:(fun visited_accum (access, (address, _trace)) ->
+        match visit_access ~f access astate visited_accum with
+        | Stop fin ->
+            Stop (Stop fin)
+        | Continue visited_accum -> (
           match visit_address address ~f (access :: rev_accesses) astate visited_accum with
           | Continue _ as cont ->
               cont
           | Stop fin ->
-            Stop (Stop fin) )
+              Stop (Stop fin) ) )
+
+
+  and visit_access ~f (access : Memory.Access.t) astate visited_accum =
+    match access with
+    | ArrayAccess (_, addr) ->
+        visit_address addr ~f [] astate visited_accum
+    | FieldAccess _ | TakeAddress | Dereference ->
+        Continue visited_accum
 
 
   let visit_address_from_var (orig_var, (address, _loc)) ~f rev_accesses astate visited_accum =

infer/src/pulse/PulseInterproc.ml

@@ -182,6 +182,9 @@ let rec materialize_pre_from_address callee_proc_name call_location ~pre ~addr_p
     | Some edges_pre ->
         Container.fold_result ~fold:Memory.Edges.fold ~init:call_state edges_pre
           ~f:(fun call_state (access_callee, (addr_pre_dest, _)) ->
+            (* HACK: we should probably visit the value in the (array) access too, but since it's
+               a value normally it shouldn't appear in the heap anyway so there should be nothing
+               to visit. *)
             let subst, access_caller = translate_access_to_caller call_state.subst access_callee in
             let astate, addr_hist_dest_caller =
               Memory.eval_edge addr_hist_caller access_caller call_state.astate