[selfInBlock] Remove false positive from mix self weakSelf

Summary: The translation of closures includes a load instruction for the captured variable, then we add that corresponding id to the closure. This doesn't correspond to an actual "use" of the captured variable in the source program though, and causes false positives. Here we remove the ids from the domain when that id is being added to a closure.

Reviewed By: ngorogiannis

Differential Revision: D19557352

fbshipit-source-id: 52b426011

infer/src/checkers/SelfInBlock.ml

@@ -246,6 +246,26 @@ module TransferFunctions = struct
     List.iter ~f:report_unchecked_strongself_issues_on_exp exps
 
 
+  (* The translation of closures includes a load instruction for the captured variable,
+     then we add that corresponding id to the closure. This doesn't correspond to an
+     actual "use" of the captured variable in the source program though, and causes false
+     positives. Here we remove the ids from the domain when that id is being added to a closure. *)
+  let remove_ids_in_closures_from_domain (domain : Domain.t) (instr : Sil.instr) =
+    let remove_id_in_closures_from_domain vars ((exp : Exp.t), _, _) =
+      match exp with Var id -> Vars.remove id vars | _ -> vars
+    in
+    let do_exp vars (exp : Exp.t) =
+      match exp with
+      | Closure {captured_vars} ->
+          List.fold ~init:vars ~f:remove_id_in_closures_from_domain captured_vars
+      | _ ->
+          vars
+    in
+    let exps = Sil.exps_of_instr instr in
+    let vars = List.fold ~init:domain.vars ~f:do_exp exps in
+    {domain with vars}
+
+
   let is_objc_instance proc_desc_opt =
     match proc_desc_opt with
     | Some proc_desc -> (
@@ -299,6 +319,7 @@ module TransferFunctions = struct
   let exec_instr (astate : Domain.t) {ProcData.summary} _cfg_node (instr : Sil.instr) =
     let attributes = Summary.get_attributes summary in
     report_unchecked_strongself_issues_on_exps astate summary instr ;
+    let astate = remove_ids_in_closures_from_domain astate instr in
     match instr with
     | Load {id; e= Lvar pvar; loc; typ} ->
         let vars =

infer/tests/codetoanalyze/objc/self-in-block/StrongSelf.m

@@ -170,7 +170,7 @@ void m2(_Nullable SelfInBlockTest* obj) {}
   };
 }
 
-- (void)wekSelfMultiple_bad {
+- (void)weakSelfMultiple_bad {
   __weak __typeof(self) weakSelf = self;
   int (^my_block)(BOOL) = ^(BOOL isTapped) {
     [weakSelf foo];
@@ -194,4 +194,15 @@ void m2(_Nullable SelfInBlockTest* obj) {}
   };
 }
 
+- (void)mixSelfWeakSelf_good:(NSArray*)resources {
+  __weak __typeof(self) weakSelf = self;
+  int (^my_block)() = ^() {
+    [self foo]; // no bug here
+    int (^my_block)() = ^() {
+      [weakSelf foo];
+      return 0;
+    };
+    return 0;
+  };
+}
 @end

infer/tests/codetoanalyze/objc/self-in-block/issues.exp

@@ -4,5 +4,5 @@ codetoanalyze/objc/self-in-block/StrongSelf.m, objc_blockSelfInBlockTest::strong
 codetoanalyze/objc/self-in-block/StrongSelf.m, objc_blockSelfInBlockTest::strongSelfCheckOnce_bad_5, 8, STRONG_SELF_NOT_CHECKED, no_bucket, ERROR, [&strongSelf assigned here,Using &strongSelf not checked for null,Using &strongSelf not checked for null,Using &strongSelf not checked for null,Using &strongSelf not checked for null]
 codetoanalyze/objc/self-in-block/StrongSelf.m, objc_blockSelfInBlockTest::strongSelfCheckOnce_bad_5, 10, STRONG_SELF_NOT_CHECKED, no_bucket, ERROR, [&strongSelf assigned here,Using &strongSelf not checked for null,Using &strongSelf not checked for null,Using &strongSelf not checked for null,Using &strongSelf not checked for null,Using &strongSelf not checked for null,Using &strongSelf not checked for null,Using &strongSelf not checked for null]
 codetoanalyze/objc/self-in-block/StrongSelf.m, objc_blockSelfInBlockTest::strongSelfNoCheckNotWeakSelf_good_2, 1, CAPTURED_STRONG_SELF, no_bucket, ERROR, [Using captured &weakSelf]
-codetoanalyze/objc/self-in-block/StrongSelf.m, objc_blockSelfInBlockTest::wekSelfMultiple_bad_11, 1, MULTIPLE_WEAKSELF, no_bucket, ERROR, [Using &weakSelf,Using &weakSelf]
+codetoanalyze/objc/self-in-block/StrongSelf.m, objc_blockSelfInBlockTest::weakSelfMultiple_bad_11, 1, MULTIPLE_WEAKSELF, no_bucket, ERROR, [Using &weakSelf,Using &weakSelf]
 codetoanalyze/objc/self-in-block/StrongSelf.m, objc_blockobjc_blockSelfInBlockTest::capturedStrongSelf_bad_12_13, 1, CAPTURED_STRONG_SELF, no_bucket, ERROR, [Using captured &strongSelf]