Add --modules=node support

tool/sdk_expected_errors.txt

Index: tool/sdk_expected_errors.txt
diff --git a/tool/sdk_expected_errors.txt b/tool/sdk_expected_errors.txt
index 2412ff6a4d435de6f11bd948465bd3bcfbbda52a..4e95e11c3a9c10ef71eec9e88b8e28f2e53d41b3 100644
--- a/tool/sdk_expected_errors.txt
+++ b/tool/sdk_expected_errors.txt
@@ -274,22 +274,22 @@ warning: [DOWN_CAST_COMPOSITE] _convertToJS ((dynamic) → dynamic) will need ru
 warning: [DOWN_CAST_COMPOSITE] super[index] (dynamic) will need runtime check to cast to type E (dart:js, line 359, col 12)
 warning: [DOWN_CAST_COMPOSITE] callMethod('splice', [index, 1])[0] (dynamic) will need runtime check to cast to type E (dart:js, line 405, col 12)
 warning: [DOWN_CAST_COMPOSITE] callMethod('pop') (dynamic) will need runtime check to cast to type E (dart:js, line 410, col 12)
-warning: [DOWN_CAST_COMPOSITE] interfaceThunk() (dynamic) will need runtime check to cast to type List<Type> (dart:_js_mirrors, line 127, col 31)
-severe: [AnalyzerMessage] The setter 'classes' is not defined for the class 'Node' (dart:html, line 5484, col 32)
-severe: [AnalyzerMessage] The method '_registerCustomElement' is not defined for the class 'HtmlDocument' (dart:html, line 8391, col 5)
-severe: [AnalyzerMessage] 14 positional arguments expected, but 18 found (dart:html, line 10953, col 185)
-severe: [AnalyzerMessage] The getter 'name' is not defined for the class 'Node' (dart:html, line 14585, col 32)
-severe: [AnalyzerMessage] The getter 'value' is not defined for the class 'Node' (dart:html, line 14597, col 34)
-severe: [INVALID_FIELD_OVERRIDE] Field declaration MutableRectangle<num>.left cannot be overridden in CssRect. (dart:html, line 15272, col 3)
-severe: [INVALID_FIELD_OVERRIDE] Field declaration MutableRectangle<num>.top cannot be overridden in CssRect. (dart:html, line 15274, col 3)
-severe: [AnalyzerMessage] The method 'matchesWithAncestors' is not defined for the class 'EventTarget' (dart:html, line 15871, col 31)
-severe: [AnalyzerMessage] The method 'matchesWithAncestors' is not defined for the class 'EventTarget' (dart:html, line 15895, col 31)
-severe: [AnalyzerMessage] Missing concrete implementation of 'EventTarget._addEventListener_1', 'EventTarget._removeEventListener_3', 'EventTarget._removeEventListener_1', 'EventTarget._removeEventListener_2' and 7 more (dart:html, line 18604, col 7)
-severe: [AnalyzerMessage] Missing concrete implementation of 'Event._stopImmediatePropagation_1', getter 'DartHtmlDomObject.raw', 'Event._preventDefault_1', setter 'DartHtmlDomObject.raw' and 4 more (dart:html, line 18752, col 7)
-severe: [AnalyzerMessage] The method 'makeLeafDispatchRecord' is not defined for the class 'KeyEvent' (dart:html, line 18798, col 12)
-severe: [AnalyzerMessage] The method 'setDispatchProperty' is not defined for the class 'KeyEvent' (dart:html, line 18868, col 5)
-severe: [AnalyzerMessage] Undefined class 'DataTransfer' (dart:html, line 18912, col 3)
-severe: [AnalyzerMessage] The getter 'clipboardData' is not defined for the class 'KeyboardEvent' (dart:html, line 18912, col 45)
+warning: [DOWN_CAST_COMPOSITE] interfaceThunk() (dynamic) will need runtime check to cast to type List<Type> (dart:_js_mirrors, line 126, col 31)
+severe: [AnalyzerMessage] The setter 'classes' is not defined for the class 'Node' (dart:html, line 5485, col 32)
+severe: [AnalyzerMessage] The method '_registerCustomElement' is not defined for the class 'HtmlDocument' (dart:html, line 8392, col 5)
+severe: [AnalyzerMessage] 14 positional arguments expected, but 18 found (dart:html, line 10954, col 185)
+severe: [AnalyzerMessage] The getter 'name' is not defined for the class 'Node' (dart:html, line 14586, col 32)
+severe: [AnalyzerMessage] The getter 'value' is not defined for the class 'Node' (dart:html, line 14598, col 34)
+severe: [INVALID_FIELD_OVERRIDE] Field declaration MutableRectangle<num>.left cannot be overridden in CssRect. (dart:html, line 15273, col 3)
+severe: [INVALID_FIELD_OVERRIDE] Field declaration MutableRectangle<num>.top cannot be overridden in CssRect. (dart:html, line 15275, col 3)
+severe: [AnalyzerMessage] The method 'matchesWithAncestors' is not defined for the class 'EventTarget' (dart:html, line 15872, col 31)
+severe: [AnalyzerMessage] The method 'matchesWithAncestors' is not defined for the class 'EventTarget' (dart:html, line 15896, col 31)
+severe: [AnalyzerMessage] Missing concrete implementation of 'EventTarget._addEventListener_1', 'EventTarget._removeEventListener_3', 'EventTarget._removeEventListener_1', 'EventTarget._removeEventListener_2' and 7 more (dart:html, line 18605, col 7)
+severe: [AnalyzerMessage] Missing concrete implementation of 'Event._stopImmediatePropagation_1', getter 'DartHtmlDomObject.raw', 'Event._preventDefault_1', setter 'DartHtmlDomObject.raw' and 4 more (dart:html, line 18753, col 7)
+severe: [AnalyzerMessage] The method 'makeLeafDispatchRecord' is not defined for the class 'KeyEvent' (dart:html, line 18799, col 12)
+severe: [AnalyzerMessage] The method 'setDispatchProperty' is not defined for the class 'KeyEvent' (dart:html, line 18869, col 5)
+severe: [AnalyzerMessage] Undefined class 'DataTransfer' (dart:html, line 18913, col 3)
+severe: [AnalyzerMessage] The getter 'clipboardData' is not defined for the class 'KeyboardEvent' (dart:html, line 18913, col 45)
 severe: [AnalyzerMessage] Missing concrete implementation of setter 'DartHtmlDomObject.raw', 'Event._initEvent_1', getter 'DartHtmlDomObject.raw', 'Event._stopImmediatePropagation_1' and 2 more (dart:html, line 18986, col 7)
 severe: [AnalyzerMessage] Undefined class 'DataTransfer' (dart:html, line 18998, col 3)
 severe: [AnalyzerMessage] The getter 'clipboardData' is not defined for the class 'Event' (dart:html, line 18998, col 45)
@@ -297,13 +297,13 @@ severe: [AnalyzerMessage] The method 'matches' is not defined for the class 'Eve
 severe: [AnalyzerMessage] The getter 'parent' is not defined for the class 'EventTarget' (dart:html, line 19045, col 23)
 severe: [AnalyzerMessage] The getter 'parent' is not defined for the class 'EventTarget' (dart:html, line 19046, col 56)
 severe: [AnalyzerMessage] Directives must appear before any declarations (dart:html, line 19449, col 1)
-severe: [AnalyzerMessage] The name 'Entry' is not a type and cannot be used as a parameterized type (dart:html, line 19515, col 44)
-severe: [AnalyzerMessage] Expected to find ';' (dart:html, line 19566, col 48)
-severe: [AnalyzerMessage] Undefined name 'console' (dart:html, line 19574, col 7)
-severe: [AnalyzerMessage] Undefined name 'console' (dart:html, line 19580, col 5)
-severe: [AnalyzerMessage] Undefined name 'js' (dart:html, line 19597, col 21)
-severe: [AnalyzerMessage] Undefined name 'js' (dart:html, line 19598, col 23)
-severe: [AnalyzerMessage] Undefined name 'js' (dart:html, line 19599, col 20)
+severe: [AnalyzerMessage] The name 'Entry' is not a type and cannot be used as a parameterized type (dart:html, line 19516, col 44)
+severe: [AnalyzerMessage] Expected to find ';' (dart:html, line 19567, col 48)
+severe: [AnalyzerMessage] Undefined name 'console' (dart:html, line 19575, col 7)
+severe: [AnalyzerMessage] Undefined name 'console' (dart:html, line 19581, col 5)
+severe: [AnalyzerMessage] Undefined name 'js' (dart:html, line 19598, col 21)
+severe: [AnalyzerMessage] Undefined name 'js' (dart:html, line 19599, col 23)
+severe: [AnalyzerMessage] Undefined name 'js' (dart:html, line 19600, col 20)
 severe: [AnalyzerMessage] The name 'File' is not defined and cannot be used in an 'is' expression (dart:html_common/conversions.dart, line 103, col 14)
 severe: [AnalyzerMessage] The name 'Blob' is not defined and cannot be used in an 'is' expression (dart:html_common/conversions.dart, line 104, col 14)
 severe: [AnalyzerMessage] The name 'FileList' is not defined and cannot be used in an 'is' expression (dart:html_common/conversions.dart, line 105, col 14)
@@ -325,44 +325,44 @@ severe: [INVALID_METHOD_OVERRIDE] Invalid override. The type of CssClassSetImpl.
 severe: [INVALID_METHOD_OVERRIDE] Invalid override. The type of CssClassSetImpl.difference ((Set<String>) → Set<String>) is not a subtype of Set<String>.difference ((Set<Object>) → Set<String>). (dart:html_common/css_class_set.dart, line 186, col 3)
 severe: [AnalyzerMessage] The argument type 'List<Node>' cannot be assigned to the parameter type 'Iterable<Element>' (dart:html_common/filtered_element_list.dart, line 34, col 25)
 severe: [STATIC_TYPE_ERROR] Type check failed: _childNodes (List<Node>) is not of type Iterable<Element> (dart:html_common/filtered_element_list.dart, line 34, col 25)
-warning: [DOWN_CAST_COMPOSITE] new List.from(_elementIterable).map((e) => e.style) (Iterable<dynamic>) will need runtime check to cast to type Iterable<CssStyleDeclaration> (dart:html, line 839, col 46)
-warning: [DOWN_CAST_COMPOSITE] wrap_jso(JS("List<Node>", "#.children", this.raw)) (dynamic) will need runtime check to cast to type List<Node> (dart:html, line 4554, col 31)
-warning: [DOWN_CAST_COMPOSITE] copy (List<dynamic>) will need runtime check to cast to type Iterable<Element> (dart:html, line 4799, col 21)
-warning: [DOWN_CAST_COMPOSITE] test ((dynamic) → bool) will need runtime check to cast to type (Element) → bool (dart:html, line 5195, col 41)
-warning: [DOWN_CAST_COMPOSITE] copy (List<dynamic>) will need runtime check to cast to type Iterable<Element> (dart:html, line 5818, col 21)
-warning: [DOWN_CAST_COMPOSITE] wrap_jso(JS("List<Node>", "#.children", this.raw)) (dynamic) will need runtime check to cast to type List<Node> (dart:html, line 7344, col 31)
-warning: [DOWN_CAST_COMPOSITE] wrap_jso(JS("List<Node>", "#.path", this.raw)) (dynamic) will need runtime check to cast to type List<Node> (dart:html, line 7646, col 26)
-warning: [DOWN_CAST_COMPOSITE] request(url, method: method, sendData: sendData).then((xhr) {return xhr.responseText;}) (Future<dynamic>) will need runtime check to cast to type Future<String> (dart:html, line 8762, col 14)
-warning: [DOWN_CAST_COMPOSITE] wrap_jso(JS("List<Node>", "#.labels", this.raw)) (dynamic) will need runtime check to cast to type List<Node> (dart:html, line 9683, col 28)
-warning: [DOWN_CAST_COMPOSITE] copy (List<dynamic>) will need runtime check to cast to type Iterable<Node> (dart:html, line 11280, col 23)
-warning: [DOWN_CAST_COMPOSITE] wrap_jso(JS('List', '#.childNodes', this.raw)) (dynamic) will need runtime check to cast to type List<Node> (dart:html, line 11362, col 32)
-warning: [DOWN_CAST_COMPOSITE] wrap_jso(JS("List<Node>", "#.children", this.raw)) (dynamic) will need runtime check to cast to type List<Node> (dart:html, line 11884, col 31)
-warning: [DOWN_CAST_COMPOSITE] wrap_jso(JS("List<Node>", "#.raw.querySelectorAll(#)", this, unwrap_jso(selectors))) (dynamic) will need runtime check to cast to type List<Node> (dart:html, line 11892, col 53)
-warning: [DOWN_CAST_COMPOSITE] _wrapZone(callback) (dynamic) will need runtime check to cast to type (num) → void (dart:html, line 12949, col 35)
-warning: [DOWN_CAST_COMPOSITE] _HEIGHT (List<dynamic>) will need runtime check to cast to type List<String> (dart:html, line 15123, col 32)
-warning: [DOWN_CAST_COMPOSITE] _WIDTH (List<dynamic>) will need runtime check to cast to type List<String> (dart:html, line 15126, col 32)
-warning: [DOWN_CAST_COMPOSITE] elementList (dynamic) will need runtime check to cast to type List<Element> (dart:html, line 15179, col 20)
-warning: [DOWN_CAST_COMPOSITE] _HEIGHT (List<dynamic>) will need runtime check to cast to type List<String> (dart:html, line 15213, col 32)
-warning: [DOWN_CAST_COMPOSITE] _WIDTH (List<dynamic>) will need runtime check to cast to type List<String> (dart:html, line 15215, col 32)
-warning: [DOWN_CAST_COMPOSITE] _HEIGHT (List<dynamic>) will need runtime check to cast to type List<String> (dart:html, line 15245, col 32)
-warning: [DOWN_CAST_COMPOSITE] _WIDTH (List<dynamic>) will need runtime check to cast to type List<String> (dart:html, line 15247, col 55)
-warning: [DOWN_CAST_COMPOSITE] e (ElementList<dynamic>) will need runtime check to cast to type Iterable<Element> (dart:html, line 15792, col 44)
-warning: [DOWN_CAST_COMPOSITE] this.where((event) => event.target.matchesWithAncestors(selector)).map((e) {e._selector = selector; return e;}) (Stream<dynamic>) will need runtime check to cast to type Stream<T> (dart:html, line 15870, col 41)
-warning: [DOWN_CAST_COMPOSITE] this.where((event) => event.target.matchesWithAncestors(selector)).map((e) {e._selector = selector; return e;}) (Stream<dynamic>) will need runtime check to cast to type Stream<T> (dart:html, line 15894, col 41)
-warning: [DOWN_CAST_COMPOSITE] pool.stream.listen(onData, onError: onError, onDone: onDone, cancelOnError: cancelOnError) (StreamSubscription<dynamic>) will need runtime check to cast to type StreamSubscription<T> (dart:html, line 15909, col 12)
-warning: [DOWN_CAST_COMPOSITE] pool.stream.listen(onData) (StreamSubscription<dynamic>) will need runtime check to cast to type StreamSubscription<T> (dart:html, line 15918, col 12)
-warning: [DOWN_CAST_COMPOSITE] _onData (dynamic) will need runtime check to cast to type (Event) → dynamic (dart:html, line 15988, col 44)
-warning: [DOWN_CAST_COMPOSITE] _onData (dynamic) will need runtime check to cast to type (Event) → dynamic (dart:html, line 15994, col 47)
-warning: [DOWN_CAST_COMPOSITE] e (ElementList<dynamic>) will need runtime check to cast to type Iterable<Element> (dart:html, line 16138, col 44)
-warning: [DOWN_CAST_COMPOSITE] attrs (dynamic) will need runtime check to cast to type Iterable<String> (dart:html, line 18059, col 9)
-warning: [DOWN_CAST_COMPOSITE] uriAttrs (dynamic) will need runtime check to cast to type Iterable<String> (dart:html, line 18060, col 9)
-warning: [DOWN_CAST_COMPOSITE] attrs (dynamic) will need runtime check to cast to type Iterable<String> (dart:html, line 18097, col 9)
-warning: [DOWN_CAST_COMPOSITE] uriAttrs (dynamic) will need runtime check to cast to type Iterable<String> (dart:html, line 18098, col 9)
-warning: [DOWN_CAST_COMPOSITE] allowedElements ?? const [] (Object) will need runtime check to cast to type Iterable<String> (dart:html, line 18230, col 33)
-warning: [DOWN_CAST_COMPOSITE] allowedAttributes ?? const [] (Object) will need runtime check to cast to type Iterable<String> (dart:html, line 18231, col 25)
-warning: [DOWN_CAST_COMPOSITE] allowedUriAttributes ?? const [] (Object) will need runtime check to cast to type Iterable<String> (dart:html, line 18232, col 28)
-warning: [DOWN_CAST_COMPOSITE] _list[index] (dynamic) will need runtime check to cast to type E (dart:html, line 18418, col 31)
-warning: [DOWN_CAST_COMPOSITE] _list.removeAt(index) (dynamic) will need runtime check to cast to type E (dart:html, line 18432, col 28)
-warning: [DOWN_CAST_COMPOSITE] _list (List<dynamic>) will need runtime check to cast to type List<Node> (dart:html, line 18448, col 29)
-warning: [DOWN_CAST_COMPOSITE] _iterator.current (dynamic) will need runtime check to cast to type E (dart:html, line 18463, col 20)
+warning: [DOWN_CAST_COMPOSITE] new List.from(_elementIterable).map((e) => e.style) (Iterable<dynamic>) will need runtime check to cast to type Iterable<CssStyleDeclaration> (dart:html, line 840, col 46)
+warning: [DOWN_CAST_COMPOSITE] wrap_jso(JS("List<Node>", "#.children", this.raw)) (dynamic) will need runtime check to cast to type List<Node> (dart:html, line 4555, col 31)
+warning: [DOWN_CAST_COMPOSITE] copy (List<dynamic>) will need runtime check to cast to type Iterable<Element> (dart:html, line 4800, col 21)
+warning: [DOWN_CAST_COMPOSITE] test ((dynamic) → bool) will need runtime check to cast to type (Element) → bool (dart:html, line 5196, col 41)
+warning: [DOWN_CAST_COMPOSITE] copy (List<dynamic>) will need runtime check to cast to type Iterable<Element> (dart:html, line 5819, col 21)
+warning: [DOWN_CAST_COMPOSITE] wrap_jso(JS("List<Node>", "#.children", this.raw)) (dynamic) will need runtime check to cast to type List<Node> (dart:html, line 7345, col 31)
+warning: [DOWN_CAST_COMPOSITE] wrap_jso(JS("List<Node>", "#.path", this.raw)) (dynamic) will need runtime check to cast to type List<Node> (dart:html, line 7647, col 26)
+warning: [DOWN_CAST_COMPOSITE] request(url, method: method, sendData: sendData).then((xhr) {return xhr.responseText;}) (Future<dynamic>) will need runtime check to cast to type Future<String> (dart:html, line 8763, col 14)
+warning: [DOWN_CAST_COMPOSITE] wrap_jso(JS("List<Node>", "#.labels", this.raw)) (dynamic) will need runtime check to cast to type List<Node> (dart:html, line 9684, col 28)
+warning: [DOWN_CAST_COMPOSITE] copy (List<dynamic>) will need runtime check to cast to type Iterable<Node> (dart:html, line 11281, col 23)
+warning: [DOWN_CAST_COMPOSITE] wrap_jso(JS('List', '#.childNodes', this.raw)) (dynamic) will need runtime check to cast to type List<Node> (dart:html, line 11363, col 32)
+warning: [DOWN_CAST_COMPOSITE] wrap_jso(JS("List<Node>", "#.children", this.raw)) (dynamic) will need runtime check to cast to type List<Node> (dart:html, line 11885, col 31)
+warning: [DOWN_CAST_COMPOSITE] wrap_jso(JS("List<Node>", "#.raw.querySelectorAll(#)", this, unwrap_jso(selectors))) (dynamic) will need runtime check to cast to type List<Node> (dart:html, line 11893, col 53)
+warning: [DOWN_CAST_COMPOSITE] _wrapZone(callback) (dynamic) will need runtime check to cast to type (num) → void (dart:html, line 12950, col 35)
+warning: [DOWN_CAST_COMPOSITE] _HEIGHT (List<dynamic>) will need runtime check to cast to type List<String> (dart:html, line 15124, col 32)
+warning: [DOWN_CAST_COMPOSITE] _WIDTH (List<dynamic>) will need runtime check to cast to type List<String> (dart:html, line 15127, col 32)
+warning: [DOWN_CAST_COMPOSITE] elementList (dynamic) will need runtime check to cast to type List<Element> (dart:html, line 15180, col 20)
+warning: [DOWN_CAST_COMPOSITE] _HEIGHT (List<dynamic>) will need runtime check to cast to type List<String> (dart:html, line 15214, col 32)
+warning: [DOWN_CAST_COMPOSITE] _WIDTH (List<dynamic>) will need runtime check to cast to type List<String> (dart:html, line 15216, col 32)
+warning: [DOWN_CAST_COMPOSITE] _HEIGHT (List<dynamic>) will need runtime check to cast to type List<String> (dart:html, line 15246, col 32)
+warning: [DOWN_CAST_COMPOSITE] _WIDTH (List<dynamic>) will need runtime check to cast to type List<String> (dart:html, line 15248, col 55)
+warning: [DOWN_CAST_COMPOSITE] e (ElementList<dynamic>) will need runtime check to cast to type Iterable<Element> (dart:html, line 15793, col 44)
+warning: [DOWN_CAST_COMPOSITE] this.where((event) => event.target.matchesWithAncestors(selector)).map((e) {e._selector = selector; return e;}) (Stream<dynamic>) will need runtime check to cast to type Stream<T> (dart:html, line 15871, col 41)
+warning: [DOWN_CAST_COMPOSITE] this.where((event) => event.target.matchesWithAncestors(selector)).map((e) {e._selector = selector; return e;}) (Stream<dynamic>) will need runtime check to cast to type Stream<T> (dart:html, line 15895, col 41)
+warning: [DOWN_CAST_COMPOSITE] pool.stream.listen(onData, onError: onError, onDone: onDone, cancelOnError: cancelOnError) (StreamSubscription<dynamic>) will need runtime check to cast to type StreamSubscription<T> (dart:html, line 15910, col 12)
+warning: [DOWN_CAST_COMPOSITE] pool.stream.listen(onData) (StreamSubscription<dynamic>) will need runtime check to cast to type StreamSubscription<T> (dart:html, line 15919, col 12)
+warning: [DOWN_CAST_COMPOSITE] _onData (dynamic) will need runtime check to cast to type (Event) → dynamic (dart:html, line 15989, col 44)
+warning: [DOWN_CAST_COMPOSITE] _onData (dynamic) will need runtime check to cast to type (Event) → dynamic (dart:html, line 15995, col 47)
+warning: [DOWN_CAST_COMPOSITE] e (ElementList<dynamic>) will need runtime check to cast to type Iterable<Element> (dart:html, line 16139, col 44)
+warning: [DOWN_CAST_COMPOSITE] attrs (dynamic) will need runtime check to cast to type Iterable<String> (dart:html, line 18060, col 9)
+warning: [DOWN_CAST_COMPOSITE] uriAttrs (dynamic) will need runtime check to cast to type Iterable<String> (dart:html, line 18061, col 9)
+warning: [DOWN_CAST_COMPOSITE] attrs (dynamic) will need runtime check to cast to type Iterable<String> (dart:html, line 18098, col 9)
+warning: [DOWN_CAST_COMPOSITE] uriAttrs (dynamic) will need runtime check to cast to type Iterable<String> (dart:html, line 18099, col 9)
+warning: [DOWN_CAST_COMPOSITE] allowedElements ?? const [] (Object) will need runtime check to cast to type Iterable<String> (dart:html, line 18231, col 33)
+warning: [DOWN_CAST_COMPOSITE] allowedAttributes ?? const [] (Object) will need runtime check to cast to type Iterable<String> (dart:html, line 18232, col 25)
+warning: [DOWN_CAST_COMPOSITE] allowedUriAttributes ?? const [] (Object) will need runtime check to cast to type Iterable<String> (dart:html, line 18233, col 28)
+warning: [DOWN_CAST_COMPOSITE] _list[index] (dynamic) will need runtime check to cast to type E (dart:html, line 18419, col 31)
+warning: [DOWN_CAST_COMPOSITE] _list.removeAt(index) (dynamic) will need runtime check to cast to type E (dart:html, line 18433, col 28)
+warning: [DOWN_CAST_COMPOSITE] _list (List<dynamic>) will need runtime check to cast to type List<Node> (dart:html, line 18449, col 29)
+warning: [DOWN_CAST_COMPOSITE] _iterator.current (dynamic) will need runtime check to cast to type E (dart:html, line 18464, col 20)
 warning: [DOWN_CAST_COMPOSITE] _validateToken ((String) → String) will need runtime check to cast to type (Object) → String (dart:html_common/css_class_set.dart, line 148, col 44)