diff --git a/pkg/compiler/lib/src/inferrer/list_tracer.dart b/pkg/compiler/lib/src/inferrer/list_tracer.dart
index db867520de1..17bb7ed4a28 100644
--- a/pkg/compiler/lib/src/inferrer/list_tracer.dart
+++ b/pkg/compiler/lib/src/inferrer/list_tracer.dart
@@ -6,6 +6,7 @@ library compiler.src.inferrer.list_tracer;
 
 import '../common/names.dart';
 import '../elements/entities.dart';
+import '../native/behavior.dart';
 import '../universe/selector.dart' show Selector;
 import '../util/util.dart' show Setlet;
 import 'node_tracer.dart';
@@ -162,10 +163,16 @@ class ListTracerVisitor extends TracerVisitor {
   @override
   visitStaticCallSiteTypeInformation(StaticCallSiteTypeInformation info) {
     super.visitStaticCallSiteTypeInformation(info);
+    final commonElements = inferrer.closedWorld.commonElements;
     MemberEntity called = info.calledElement;
-    if (inferrer.closedWorld.commonElements.isForeign(called) &&
-        called.name == Identifiers.JS) {
-      bailout('Used in JS ${info.debugName}');
+    if (commonElements.isForeign(called) && called.name == Identifiers.JS) {
+      NativeBehavior nativeBehavior = inferrer.closedWorld.elementMap
+          .getNativeBehaviorForJsCall(info.invocationNode);
+      // Assume side-effects means that the list has escaped to some unknown
+      // location.
+      if (nativeBehavior.sideEffects.hasSideEffects()) {
+        bailout('Used in JS ${info.debugName}');
+      }
     }
   }
 
diff --git a/pkg/compiler/lib/src/inferrer/type_graph_nodes.dart b/pkg/compiler/lib/src/inferrer/type_graph_nodes.dart
index 365500e6e9d..78664ebac93 100644
--- a/pkg/compiler/lib/src/inferrer/type_graph_nodes.dart
+++ b/pkg/compiler/lib/src/inferrer/type_graph_nodes.dart
@@ -968,6 +968,8 @@ class StaticCallSiteTypeInformation extends CallSiteTypeInformation {
       : super(abstractValueDomain, context, call, enclosing, selector,
             arguments, inLoop);
 
+  ir.StaticInvocation get invocationNode => _call as ir.StaticInvocation;
+
   MemberTypeInformation _getCalledTypeInfo(InferrerEngine inferrer) {
     return inferrer.types.getInferredTypeOfMember(calledElement);
   }
diff --git a/pkg/compiler/test/inference/data/closure_tracer.dart b/pkg/compiler/test/inference/data/closure_tracer.dart
index 08105f70dc7..edccdb3193a 100644
--- a/pkg/compiler/test/inference/data/closure_tracer.dart
+++ b/pkg/compiler/test/inference/data/closure_tracer.dart
@@ -51,22 +51,22 @@ testStoredInInstance() {
   return res;
 }
 
-/*member: testStoredInMapOfList:[null|subclass=Object]*/
+/*member: testStoredInMapOfList:[null|exact=JSUInt31]*/
 testStoredInMapOfList() {
   var res;
-  /*[null|subclass=Object]*/ closure(/*[null|subclass=Object]*/ a) => res = a;
+  /*[exact=JSUInt31]*/ closure(/*[exact=JSUInt31]*/ a) => res = a;
   dynamic a = <dynamic>[closure];
   dynamic b = <dynamic, dynamic>{'foo': 1};
 
   b
-      /*update: Dictionary([subclass=JsLinkedHashMap], key: [exact=JSString], value: Union(null, [exact=JSExtendableArray], [exact=JSUInt31]), map: {foo: [exact=JSUInt31], bar: Container([null|exact=JSExtendableArray], element: [null|subclass=Object], length: null)})*/
+      /*update: Dictionary([subclass=JsLinkedHashMap], key: [exact=JSString], value: Union(null, [exact=JSExtendableArray], [exact=JSUInt31]), map: {foo: [exact=JSUInt31], bar: Container([null|exact=JSExtendableArray], element: [subclass=Closure], length: 1)})*/
       ['bar'] = a;
 
   b
-          /*Dictionary([subclass=JsLinkedHashMap], key: [exact=JSString], value: Union(null, [exact=JSExtendableArray], [exact=JSUInt31]), map: {foo: [exact=JSUInt31], bar: Container([null|exact=JSExtendableArray], element: [null|subclass=Object], length: null)})*/
+          /*Dictionary([subclass=JsLinkedHashMap], key: [exact=JSString], value: Union(null, [exact=JSExtendableArray], [exact=JSUInt31]), map: {foo: [exact=JSUInt31], bar: Container([null|exact=JSExtendableArray], element: [subclass=Closure], length: 1)})*/
           ['bar']
 
-      /*Container([null|exact=JSExtendableArray], element: [null|subclass=Object], length: null)*/
+      /*Container([null|exact=JSExtendableArray], element: [subclass=Closure], length: 1)*/
       [0](42);
   return res;
 }
diff --git a/pkg/compiler/test/inference/data/list_js.dart b/pkg/compiler/test/inference/data/list_js.dart
new file mode 100644
index 00000000000..9b640606357
--- /dev/null
+++ b/pkg/compiler/test/inference/data/list_js.dart
@@ -0,0 +1,60 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Test effect of NativeBehavior on list tracing.
+
+/// ignore: IMPORT_INTERNAL_LIBRARY
+import 'dart:_foreign_helper' show JS;
+
+/*member: main:[null]*/
+main() {
+  test1();
+  test2();
+  test3();
+  test4();
+}
+
+/*member: test1:[null]*/
+test1() {
+  var list = [42];
+  JS('', '#', list); // '#' is by default a no-op.
+  witness1(list);
+}
+
+/*member: witness1:[null]*/
+witness1(
+    /*Container([exact=JSExtendableArray], element: [exact=JSUInt31], length: 1)*/ x) {}
+
+/*member: test2:[null]*/
+test2() {
+  var list = [42];
+  JS('effects:all;depends:all', '#', list);
+  witness2(list);
+}
+
+/*member: witness2:[null]*/
+witness2(
+    /*Container([exact=JSExtendableArray], element: [null|subclass=Object], length: null)*/ x) {}
+
+/*member: test3:[null]*/
+test3() {
+  var list = [42];
+  JS('', '#.slice(0)', list);
+  witness3(list);
+}
+
+/*member: witness3:[null]*/
+witness3(
+    /*Container([exact=JSExtendableArray], element: [null|subclass=Object], length: null)*/ x) {}
+
+/*member: test4:[null]*/
+test4() {
+  var list = [42];
+  JS('effects:none;depends:all', '#.slice(0)', list);
+  witness4(list);
+}
+
+/*member: witness4:[null]*/
+witness4(
+    /*Container([exact=JSExtendableArray], element: [exact=JSUInt31], length: 1)*/ x) {}
diff --git a/pkg/compiler/test/inference/data/map_tracer_keys.dart b/pkg/compiler/test/inference/data/map_tracer_keys.dart
index 20e469e8c96..3f183a6adca 100644
--- a/pkg/compiler/test/inference/data/map_tracer_keys.dart
+++ b/pkg/compiler/test/inference/data/map_tracer_keys.dart
@@ -79,28 +79,28 @@ test2() {
 /*member: aDouble3:Union(null, [exact=JSDouble], [exact=JSExtendableArray])*/
 dynamic aDouble3 = 42.5;
 
-/*member: aList3:Container([exact=JSExtendableArray], element: [null|subclass=Object], length: null)*/
+/*member: aList3:Container([exact=JSExtendableArray], element: [exact=JSUInt31], length: 1)*/
 dynamic aList3 = [42];
 
-/*member: consume3:Container([exact=JSExtendableArray], element: [null|subclass=Object], length: null)*/
+/*member: consume3:Container([exact=JSExtendableArray], element: [exact=JSUInt31], length: 1)*/
 consume3(
-        /*Container([exact=JSExtendableArray], element: [null|subclass=Object], length: null)*/ x) =>
+        /*Container([exact=JSExtendableArray], element: [exact=JSUInt31], length: 1)*/ x) =>
     x;
 
 /*member: test3:[null]*/
 test3() {
   dynamic theMap = <dynamic, dynamic>{'a': 2.2, 'b': 3.3, 'c': 4.4};
   theMap
-      /*update: Dictionary([subclass=JsLinkedHashMap], key: [exact=JSString], value: Union(null, [exact=JSDouble], [exact=JSExtendableArray]), map: {a: [exact=JSDouble], b: [exact=JSDouble], c: [exact=JSDouble], d: Container([null|exact=JSExtendableArray], element: [null|subclass=Object], length: null)})*/
+      /*update: Dictionary([subclass=JsLinkedHashMap], key: [exact=JSString], value: Union(null, [exact=JSDouble], [exact=JSExtendableArray]), map: {a: [exact=JSDouble], b: [exact=JSDouble], c: [exact=JSDouble], d: Container([null|exact=JSExtendableArray], element: [exact=JSUInt31], length: 1)})*/
       ['d'] = aList3;
   /*iterator: [exact=LinkedHashMapKeyIterable]*/
   /*current: [exact=LinkedHashMapKeyIterator]*/
   /*moveNext: [exact=LinkedHashMapKeyIterator]*/
   for (var key in theMap.
-      /*Dictionary([subclass=JsLinkedHashMap], key: [exact=JSString], value: Union(null, [exact=JSDouble], [exact=JSExtendableArray]), map: {a: [exact=JSDouble], b: [exact=JSDouble], c: [exact=JSDouble], d: Container([null|exact=JSExtendableArray], element: [null|subclass=Object], length: null)})*/
+      /*Dictionary([subclass=JsLinkedHashMap], key: [exact=JSString], value: Union(null, [exact=JSDouble], [exact=JSExtendableArray]), map: {a: [exact=JSDouble], b: [exact=JSDouble], c: [exact=JSDouble], d: Container([null|exact=JSExtendableArray], element: [exact=JSUInt31], length: 1)})*/
       keys) {
     aDouble3 = theMap
-        /*Dictionary([subclass=JsLinkedHashMap], key: [exact=JSString], value: Union(null, [exact=JSDouble], [exact=JSExtendableArray]), map: {a: [exact=JSDouble], b: [exact=JSDouble], c: [exact=JSDouble], d: Container([null|exact=JSExtendableArray], element: [null|subclass=Object], length: null)})*/
+        /*Dictionary([subclass=JsLinkedHashMap], key: [exact=JSString], value: Union(null, [exact=JSDouble], [exact=JSExtendableArray]), map: {a: [exact=JSDouble], b: [exact=JSDouble], c: [exact=JSDouble], d: Container([null|exact=JSExtendableArray], element: [exact=JSUInt31], length: 1)})*/
         [key];
   }
   // We have to reference it somewhere, so that it always gets resolved.
diff --git a/pkg/compiler/test/inference/list_tracer_test.dart b/pkg/compiler/test/inference/list_tracer_test.dart
index 96583746b39..4e23f1b4f33 100644
--- a/pkg/compiler/test/inference/list_tracer_test.dart
+++ b/pkg/compiler/test/inference/list_tracer_test.dart
@@ -237,9 +237,7 @@ doTest(String allocation, {bool nullify}) async {
   checkType('listEscapingInSetterValue', commonMasks.numType);
   checkType('listEscapingInIndex', commonMasks.numType);
   checkType('listEscapingInIndexSet', commonMasks.uint31Type);
-  // TODO(johnniwinther): Since Iterable.iterableToString is part of the closed
-  // world we find the `dynamicType` instead of `numType`.
-  checkType('listEscapingTwiceInIndexSet', commonMasks.dynamicType);
+  checkType('listEscapingTwiceInIndexSet', commonMasks.numType);
   checkType('listSetInNonFinalField', commonMasks.numType);
   checkType('listWithChangedLength', commonMasks.uint31Type.nullable());
 
diff --git a/sdk/lib/_internal/js_runtime/lib/core_patch.dart b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
index 2b48b5dc0cf..1cd3bc414d8 100644
--- a/sdk/lib/_internal/js_runtime/lib/core_patch.dart
+++ b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
@@ -26,7 +26,7 @@ import 'dart:_js_helper'
         getTraceFromException,
         RuntimeError;
 
-import 'dart:_foreign_helper' show JS, JS_GET_FLAG;
+import 'dart:_foreign_helper' show JS;
 import 'dart:_native_typed_data' show NativeUint8List;
 import 'dart:_rti' show getRuntimeType;
 
@@ -459,9 +459,15 @@ class List<E> {
     assertUnreachable();
   }
 
+  factory List._ofArray(Iterable<E> elements) {
+    return JSArray<E>.markGrowable(
+        JS('effects:none;depends:no-static', '#.slice(0)', elements));
+  }
+
   factory List._of(Iterable<E> elements) {
-    // This is essentially `addAll`, but without a check for modifiability or
-    // ConcurrentModificationError on the receiver.
+    if (elements is JSArray) return List._ofArray(elements);
+    // This is essentially `<E>[]..addAll(elements)`, but without a check for
+    // modifiability or ConcurrentModificationError on the receiver.
     List<E> list = <E>[];
     for (final e in elements) {
       list.add(e);