Change length of Dsizeof from an exp to a dexp

Summary: Change length of Dsizeof from an exp to a dexp.  This make a little progress toward reducing the types that must be mutually recursive with exp.

Reviewed By: sblackshear

Differential Revision: D3541337

fbshipit-source-id: 95d1f70

infer/src/IR/Sil.re

@@ -420,7 +420,7 @@ type dexp =
   | Darray of dexp dexp
   | Dbinop of binop dexp dexp
   | Dconst of const
-  | Dsizeof of Typ.t (option exp) Subtype.t
+  | Dsizeof of Typ.t (option dexp) Subtype.t
   | Dderef of dexp
   | Dfcall of dexp (list dexp) Location.t call_flags
   | Darrow of dexp Ident.fieldname

infer/src/IR/Sil.rei

@@ -147,7 +147,7 @@ type dexp =
   | Darray of dexp dexp
   | Dbinop of binop dexp dexp
   | Dconst of const
-  | Dsizeof of Typ.t (option exp) Subtype.t
+  | Dsizeof of Typ.t (option dexp) Subtype.t
   | Dderef of dexp
   | Dfcall of dexp (list dexp) Location.t call_flags
   | Darrow of dexp Ident.fieldname

infer/src/backend/errdesc.ml

@@ -387,7 +387,7 @@ and _exp_rv_dexp (_seen : Sil.ExpSet.t) node e : Sil.dexp option =
         _exp_rv_dexp seen node e1
     | Sil.Sizeof (typ, len, sub) ->
         if verbose then (L.d_str "exp_rv_dexp: type "; Sil.d_exp e; L.d_ln ());
-        Some (Sil.Dsizeof (typ, len, sub))
+        Some (Sil.Dsizeof (typ, Option.map_default (_exp_rv_dexp seen node) None len, sub))
     | _ ->
         if verbose then (L.d_str "exp_rv_dexp: no match for  "; Sil.d_exp e; L.d_ln ());
         None