[ConfigImpact] Address unknown ObjC init methods as cheap

Summary: We have some FPs due to unknown init methods that are added dynamically.

Reviewed By: ezgicicek

Differential Revision: D27856371

fbshipit-source-id: b6fb46df3

infer/src/IR/Procname.ml

@@ -357,9 +357,9 @@ module ObjC_Cpp = struct
     if is_instance then ObjCInstanceMethod else ObjCClassMethod
 
 
-  let is_objc_constructor method_name =
+  let is_prefix_init s = String.is_prefix ~prefix:"init" s
-    String.equal method_name "new" || String.is_prefix ~prefix:"init" method_name
 
+  let is_objc_constructor method_name = String.equal method_name "new" || is_prefix_init method_name
 
   let is_objc_kind = function
     | ObjCClassMethod | ObjCInstanceMethod | ObjCInternalMethod ->
@@ -605,6 +605,12 @@ let is_objc_dealloc procname =
   match procname with ObjC_Cpp {method_name} -> ObjC_Cpp.is_objc_dealloc method_name | _ -> false
 
 
+let is_objc_init procname =
+  is_objc_method procname
+  &&
+  match procname with ObjC_Cpp {method_name} -> ObjC_Cpp.is_prefix_init method_name | _ -> false
+
+
 let block_of_procname procname =
   match procname with
   | Block block ->

infer/src/IR/Procname.mli

@@ -326,6 +326,9 @@ val is_cpp_lambda : t -> bool
 val is_objc_dealloc : t -> bool
 (** Return whether the dealloc method of an Objective-C class. *)
 
+val is_objc_init : t -> bool
+(** Return whether the init method of an Objective-C class. *)
+
 val is_c_method : t -> bool
 (** Return true this is an Objective-C/C++ method name. *)
 

infer/src/cost/ConfigImpactAnalysis.ml

@@ -447,6 +447,9 @@ module Dom = struct
             join_unchecked_callees
               (UncheckedCallees.replace_location_by_call location callee_summary)
               (UncheckedCalleesCond.replace_location_by_call location callee_summary_cond)
+        | None when Procname.is_objc_init callee ->
+            (* If callee is unknown ObjC initializer, ignore it. *)
+            astate
         | _ ->
             (* Otherwise, add callee's name. *)
             join_unchecked_callees