Use a symbol for static length/name (conflicts with Function properties in ES5: cannot redefine Function.name/length properties) (issue #312)

Author: Olivier Chafik

lib/runtime/dart/_internal.js

@@ -1862,7 +1862,7 @@ dart_library.library('dart/_internal', null, /* Imports */[
     static change() {
       return new core.UnsupportedError("Cannot change the content of an unmodifiable List");
     }
-    static length() {
+    static [dartx.length]() {
       return new core.UnsupportedError("Cannot change length of unmodifiable List");
     }
     static remove() {
@@ -1873,16 +1873,16 @@ dart_library.library('dart/_internal', null, /* Imports */[
     statics: () => ({
       add: [core.UnsupportedError, []],
       change: [core.UnsupportedError, []],
-      length: [core.UnsupportedError, []],
+      [dartx.length]: [core.UnsupportedError, []],
       remove: [core.UnsupportedError, []]
     }),
-    names: ['add', 'change', 'length', 'remove']
+    names: ['add', 'change', dartx.length, 'remove']
   });
   class NonGrowableListError extends core.Object {
     static add() {
       return new core.UnsupportedError("Cannot add to non-growable List");
     }
-    static length() {
+    static [dartx.length]() {
       return new core.UnsupportedError("Cannot change length of non-growable List");
     }
     static remove() {
@@ -1892,10 +1892,10 @@ dart_library.library('dart/_internal', null, /* Imports */[
   dart.setSignature(NonGrowableListError, {
     statics: () => ({
       add: [core.UnsupportedError, []],
-      length: [core.UnsupportedError, []],
+      [dartx.length]: [core.UnsupportedError, []],
       remove: [core.UnsupportedError, []]
     }),
-    names: ['add', 'length', 'remove']
+    names: ['add', dartx.length, 'remove']
   });
   function makeListFixedLength(growableList) {
     _interceptors.JSArray.markFixedList(growableList);

lib/runtime/dart/collection.js

@@ -2440,7 +2440,7 @@ dart_library.library('dart/collection', null, /* Imports */[
     static getValues(map) {
       return map.keys[dartx.map](dart.fn(key => map.get(key)));
     }
-    static length(map) {
+    static [dartx.length](map) {
       return map.keys[dartx.length];
     }
     static isEmpty(map) {
@@ -2507,15 +2507,15 @@ dart_library.library('dart/collection', null, /* Imports */[
       clear: [dart.dynamic, [core.Map]],
       forEach: [dart.dynamic, [core.Map, dart.functionType(dart.void, [dart.dynamic, dart.dynamic])]],
       getValues: [core.Iterable, [core.Map]],
-      length: [core.int, [core.Map]],
+      [dartx.length]: [core.int, [core.Map]],
       isEmpty: [core.bool, [core.Map]],
       isNotEmpty: [core.bool, [core.Map]],
       mapToString: [core.String, [core.Map]],
       _id: [dart.dynamic, [dart.dynamic]],
       _fillMapWithMappedIterable: [dart.void, [core.Map, core.Iterable, dart.functionType(dart.dynamic, [dart.dynamic]), dart.functionType(dart.dynamic, [dart.dynamic])]],
       _fillMapWithIterables: [dart.void, [core.Map, core.Iterable, core.Iterable]]
     }),
-    names: ['containsValue', 'containsKey', 'putIfAbsent', 'clear', 'forEach', 'getValues', 'length', 'isEmpty', 'isNotEmpty', 'mapToString', '_id', '_fillMapWithMappedIterable', '_fillMapWithIterables']
+    names: ['containsValue', 'containsKey', 'putIfAbsent', 'clear', 'forEach', 'getValues', dartx.length, 'isEmpty', 'isNotEmpty', 'mapToString', '_id', '_fillMapWithMappedIterable', '_fillMapWithIterables']
   });
   const Queue$ = dart.generic(function(E) {
     class Queue extends core.Object {

lib/src/codegen/js_codegen.dart

@@ -3391,8 +3391,13 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ClosureAnnotator {
       bool unary: false,
       bool isStatic: false,
       bool allowExtensions: true}) {
-    // Static members skip the rename steps.
-    if (isStatic) return _propertyName(name);
+    // Static members skip the rename steps, except for Function properties.
+    if (isStatic) {
+      if (name == 'length' || name == 'name') {
+        return js.call('dartx.#', _propertyName(name));
+      }
+      return _propertyName(name);
+    }
 
     if (name.startsWith('_')) {
       return _privateNames.putIfAbsent(