Adding Support For Instof Subtype (#1447)

Summary:
This complements a bug fix for InferSharp in which we weren't handling type-checking correctly.

Pull Request resolved: https://github.com/facebook/infer/pull/1447

Reviewed By: ngorogiannis

Differential Revision: D28772069

Pulled By: jvillard

fbshipit-source-id: be0210836

infer/src/backend/InferAnalyzeJson.ml

@@ -293,8 +293,10 @@ and parse_exp (json : Safe.t) =
     match s with
     | "exact" ->
         Exp.Sizeof {typ= t; nbytes= None; dynamic_length= None; subtype= Subtype.exact}
+    | "instof" ->
+        Exp.Sizeof {typ= t; nbytes= None; dynamic_length= None; subtype= Subtype.subtypes_instof}
     | _ ->
-        Logging.die InternalError "Subtype in Sizeof instruction is not 'exact'"
+        Logging.die InternalError "Subtype in Sizeof instruction is not supported."
   else Logging.die InternalError "Unknown expression kind %s" ekind