[checkers] kill ref in abstract interpreter

Reviewed By: jeremydubreil

Differential Revision: D3972931

fbshipit-source-id: f435997

infer/src/checkers/abstractInterpreter.ml

@@ -119,14 +119,15 @@ module MakeNoCFG
   module Interprocedural (Summ : Summary.S with type summary = A.astate) = struct
 
     let checker { Callbacks.get_proc_desc; proc_desc; proc_name; tenv; } extras =
-      let post_opt = ref None in
-      let analyze_ondemand _source pdesc =
+      let analyze_ondemand_ _ pdesc =
         match compute_post (ProcData.make pdesc tenv extras) with
         | Some post ->
             Summ.write_summary (Cfg.Procdesc.get_proc_name pdesc) post;
-            post_opt := Some post
+            Some post
         | None ->
-            post_opt := None in
+            None in
+      let analyze_ondemand source pdesc =
+        ignore (analyze_ondemand_ source pdesc) in
       let callbacks =
         {
           Ondemand.analyze_ondemand;
@@ -136,10 +137,11 @@ module MakeNoCFG
       then
         begin
           Ondemand.set_callbacks callbacks;
-          analyze_ondemand DB.source_file_empty proc_desc;
+          let post_opt = analyze_ondemand_ DB.source_file_empty proc_desc in
           Ondemand.unset_callbacks ();
-        end;
-      !post_opt
+          post_opt
+        end
+      else None
   end
 end