[cost] Fix on-demand generation of NSEnumerator

Summary: This diff fixes on-demand symbolic value generation of a class that inherits NSEnumerator.

Reviewed By: ngorogiannis

Differential Revision: D24504955

fbshipit-source-id: bcb20e8aa

infer/src/bufferoverrun/bufferOverrunDomain.ml

@@ -563,7 +563,8 @@ module Val = struct
         itv_val ~non_int:false |> set_itv_updated_by_addition
     | Tptr ({desc= Tfun}, _) ->
         of_func_ptrs (FuncPtr.Set.of_path path)
-    | Tptr ({desc= Tstruct name}, _) when Typ.equal_name name Typ.Name.Objc.objc_ns_enumerator ->
+    | Tptr ({desc= Tstruct name}, _)
+      when PatternMatch.is_subtype tenv name Typ.Name.Objc.objc_ns_enumerator ->
         (* NOTE: It generates a value of NSEnumerator specifically.  Especially, it assigns zero to
            the offset, rather than a symbol, to avoid precision loss by limited handling of symbolic
            values in the domain.  Although this is an unsound design choice, we expect it should not

infer/tests/codetoanalyze/objc/performance/NSArray.m

@@ -220,3 +220,10 @@ void call_my_enumerator_next_object_linear(MyEnumerator* enumerator) {
   // NSEnumerator.nextObject should be replaced to MyEnumerator.nextObject
   NSString* s = [enumerator nextObject];
 }
+
+// The cost analyzer cannot reason the amortized complexity.
+void loop_with_my_enumerator_next_object_linear_FP(MyEnumerator* enumerator) {
+  NSString* s;
+  while (s = [enumerator nextObject]) {
+  }
+}

infer/tests/codetoanalyze/objc/performance/cost-issues.exp

@@ -1,8 +1,9 @@
 ${XCODE_ISYSROOT}/System/Library/Frameworks/Foundation.framework/Headers/NSArray.h, NSArray.indexOfObject:inSortedRange:options:usingComparator:[objc_blocknsarray_binary_search_log_FN_1], 0,  OnUIThread:false, []
 codetoanalyze/objc/performance/MyEnumerator.m, MyEnumerator.dealloc, 1,  OnUIThread:false, []
-codetoanalyze/objc/performance/MyEnumerator.m, MyEnumerator.nextObject, 6 + 3 ⋅ self->n + 3 ⋅ (1+max(0, self->n)),  OnUIThread:false, [{1+max(0, self->n)},Loop,{self->n},Loop]
+codetoanalyze/objc/performance/MyEnumerator.m, MyEnumerator.nextObject, 6 + 3 ⋅ self->n.ub + 3 ⋅ (1+max(0, self->n.ub)),  OnUIThread:false, [{1+max(0, self->n.ub)},Loop,{self->n.ub},Loop]
 codetoanalyze/objc/performance/NSArray.m, call_my_enumerator_next_object_linear, 9 + 3 ⋅ enumerator->n.ub + 3 ⋅ (1+max(0, enumerator->n.ub)),  OnUIThread:false, [{1+max(0, enumerator->n.ub)},Call to MyEnumerator.nextObject,Loop,{enumerator->n.ub},Call to MyEnumerator.nextObject,Loop]
 codetoanalyze/objc/performance/NSArray.m, call_nsarray_enumerator_param_linear, 6,  OnUIThread:false, []
+codetoanalyze/objc/performance/NSArray.m, loop_with_my_enumerator_next_object_linear_FP, 2 + 3 ⋅ enumerator->n.ub × (enumerator.length + 1) + 10 ⋅ (enumerator.length + 1) + 3 ⋅ (enumerator.length + 1) × (1+max(0, enumerator->n.ub)),  OnUIThread:false, [{1+max(0, enumerator->n.ub)},Call to MyEnumerator.nextObject,Loop,{enumerator.length + 1},Loop,{enumerator.length + 1},Loop,{enumerator->n.ub},Call to MyEnumerator.nextObject,Loop]
 codetoanalyze/objc/performance/NSArray.m, multiple_nsarray_enumerators_param_linear, 12 + 5 ⋅ (enumerator2.length + enumerator1.length + 2),  OnUIThread:false, [{enumerator2.length + enumerator1.length + 2},Loop]
 codetoanalyze/objc/performance/NSArray.m, nsarray_access_constant, 50,  OnUIThread:false, []
 codetoanalyze/objc/performance/NSArray.m, nsarray_access_linear, 3 + 7 ⋅ array->elements.length.ub + 3 ⋅ (array->elements.length.ub + 1),  OnUIThread:false, [{array->elements.length.ub + 1},Loop,{array->elements.length.ub},Loop]