[cost] Fix function name matching

Summary: `Str.regexp_string` should be used to find a method name instead of `Str.regexp`.

Reviewed By: ezgicicek

Differential Revision: D18136598

fbshipit-source-id: c4b56dd64

infer/src/IR/Typ.ml

@@ -1136,7 +1136,7 @@ module Procname = struct
   let is_infer_undefined pn =
     match pn with
     | Java j ->
-        let regexp = Str.regexp "com.facebook.infer.builtins.InferUndefined" in
+        let regexp = Str.regexp_string "com.facebook.infer.builtins.InferUndefined" in
         Str.string_match regexp (Java.get_class_name j) 0
     | _ ->
         (* TODO: add cases for obj-c, c, c++ *)

infer/src/backend/Differential.ml

@@ -213,7 +213,7 @@ let issue_of_cost kind CostIssues.{complexity_increase_issue; zero_issue; infini
   let file = cost_info.Jsonbug_t.loc.file in
   let method_name = cost_info.Jsonbug_t.procedure_name in
   let class_name =
-    match Str.split (Str.regexp ("." ^ method_name)) cost_info.Jsonbug_t.procedure_id with
+    match Str.split (Str.regexp_string ("." ^ method_name)) cost_info.Jsonbug_t.procedure_id with
     | [class_name; _] ->
         class_name
     | _ ->