[infer][nullable checker] no longer propagate the nullability when the lhs is not a pointer type

Summary: The checker should only propagate the nullablility on the lhs when of pointer type.

Reviewed By: sblackshear

Differential Revision: D6630294

fbshipit-source-id: 07fe3d6

infer/src/checkers/NullabilityCheck.ml

@@ -221,8 +221,13 @@ module TransferFunctions (CFG : ProcCfg.S) = struct
         check_ap proc_data loc receiver astate
     | Call (_, Direct callee_pname, args, _, loc) when is_objc_container_add_method callee_pname ->
         check_nil_in_objc_container proc_data loc args astate
-    | Call (Some ret_var, Direct callee_pname, (HilExp.AccessPath receiver) :: _, _, _)
-      when is_objc_instance_method callee_pname -> (
+    | Call
+        ( Some ((_, ret_typ) as ret_var)
+        , Direct callee_pname
+        , (HilExp.AccessPath receiver) :: _
+        , _
+        , _ )
+      when Typ.is_pointer ret_typ && is_objc_instance_method callee_pname -> (
       match longest_nullable_prefix receiver astate with
       | None ->
           astate

infer/tests/codetoanalyze/objc/nullable/Examples.m

@@ -10,8 +10,15 @@
 
 int* __nullable returnsNull();
 
+typedef struct s_ {
+  int x;
+} S;
+
 @interface T : NSObject
 - (NSObject* _Nullable)nullableMethod;
+- (T* _Nullable)nullableT;
+@property(nonatomic) S structProperty;
+@property(nonatomic) S* pointerProperty;
 @end
 
 @implementation T {
@@ -216,6 +223,28 @@ int* __nullable returnsNull();
   return mutableArray;
 }
 
+- (NSArray*)propagateNullabilityOnMethodCallBad {
+  NSObject* nullableObject = [self nullableMethod];
+  NSString* nullableString =
+      [nullableObject description]; // returns nil if nullableObject is nil
+  return @[ nullableString ]; // reports here
+}
+
+- (S*)shouldPropagateNullabilityOnPointerTypeBad {
+  T* nullableT = [self nullableT];
+  S* s = nullableT.pointerProperty; // returns  nil when nullableT is nil
+  s->x = 42; // reports here
+  return s;
+}
+
+- (S)shouldNotPropagateNullabilityOnNonPointerTypeGood {
+  T* nullableT = [self nullableT];
+  S s =
+      nullableT.structProperty; // returns an empty struct when nullabeT is nil
+  s.x = 42; // does not report here
+  return s;
+}
+
 @end
 
 @protocol P

infer/tests/codetoanalyze/objc/nullable/issues.exp

@@ -14,8 +14,10 @@ codetoanalyze/objc/nullable/Examples.m, T_nullableObjectInNSArrayBad, 2, NULLABL
 codetoanalyze/objc/nullable/Examples.m, T_nullableValueInNSDictionaryBad, 2, NULLABLE_DEREFERENCE, [dereference of &nullableValue,assignment of the nullable value,definition of nullableMethod]
 codetoanalyze/objc/nullable/Examples.m, T_nullableValueInNSDictionaryInitBad, 2, NULLABLE_DEREFERENCE, [dereference of &nullableValue,assignment of the nullable value,definition of nullableMethod]
 codetoanalyze/objc/nullable/Examples.m, T_nullableValueInNSDictionaryInitLiteralBad, 2, NULLABLE_DEREFERENCE, [dereference of &nullableValue,assignment of the nullable value,definition of nullableMethod]
+codetoanalyze/objc/nullable/Examples.m, T_propagateNullabilityOnMethodCallBad, 4, NULLABLE_DEREFERENCE, [dereference of &nullableString,assignment of the nullable value,definition of nullableMethod]
 codetoanalyze/objc/nullable/Examples.m, T_secondElementNullableObjectInNSArrayBad, 3, NULLABLE_DEREFERENCE, [dereference of &nullableObject,assignment of the nullable value,definition of nullableMethod]
 codetoanalyze/objc/nullable/Examples.m, T_setNullableObjectInDictionaryBad, 2, NULLABLE_DEREFERENCE, [dereferencing the return of nullableMethod,assignment of the nullable value,definition of nullableMethod]
+codetoanalyze/objc/nullable/Examples.m, T_shouldPropagateNullabilityOnPointerTypeBad, 3, NULLABLE_DEREFERENCE, [dereference of &s,assignment of the nullable value,definition of nullableT]
 codetoanalyze/objc/nullable/Examples.m, T_testNonnullFieldForNullBad, 1, FIELD_SHOULD_BE_NULLABLE, [Field nonnullField is compared to null here]
 codetoanalyze/objc/nullable/Examples.m, T_testUnnanotatedFieldForNullBad, 1, FIELD_SHOULD_BE_NULLABLE, [Field unnanotatedField is compared to null here]
 codetoanalyze/objc/nullable/Examples.m, callNullableMethodFromProtocolBad, 2, NULLABLE_DEREFERENCE, [dereference of &nullableObject,assignment of the nullable value,definition of nullableMethod]