optimize extension member symbols in DDC, issue #30531

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/classes.dart

 // Copyright (c) 2015, 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.
 
 /// This library defines the operations that define and manipulate Dart
 /// classes.  Included in this are:
 ///   - Generics
 ///   - Class metadata
 ///   - Extension methods
 ///
@@ skipping 373 matching lines @@
 bool hasSetter(type, name) => _hasSigEntry(type, _setterSig, name);
 bool hasField(type, name) => _hasSigEntry(type, _fieldSig, name);
 
 final _extensionType = JS('', 'Symbol("extensionType")');
 
 /// This assumes that obj is not null
 getExtensionType(obj) => JS('', '#[#]', obj, _extensionType);
 
 final dartx = JS('', 'dartx');
 
-getExtensionSymbol(name) {
-  var sym = JS('', 'dartx[#]', name);
-  if (sym == null) {
-    sym = JS('', 'Symbol("dartx." + #.toString())', name);
-    JS('', 'dartx[#] = #', name, sym);
-  }
-  return sym;
-}
-
-defineExtensionNames(names) =>
-    JS('', '#.forEach(#)', names, getExtensionSymbol);
-
 /// Install properties in prototype-first order.  Properties / descriptors from
 /// more specific types should overwrite ones from less specific types.
 void _installProperties(jsProto, dartType, installedParent) {
   if (JS('bool', '# === #', dartType, Object)) {
     _installPropertiesForObject(jsProto);
     return;
   }
   // If the extension methods of the parent have been installed on the parent
   // of [jsProto], the methods will be available via prototype inheritance.
   var dartSupertype = JS('', '#.__proto__', dartType);
   if (JS('bool', '# !== #', dartSupertype, installedParent)) {
     _installProperties(jsProto, dartSupertype, installedParent);
   }
 
   var dartProto = JS('', '#.prototype', dartType);
   copyTheseProperties(jsProto, dartProto, getOwnPropertySymbols(dartProto));
 }
 
 void _installPropertiesForObject(jsProto) {
   // core.Object members need to be copied from the non-symbol name to the
   // symbol name.
   var coreObjProto = JS('', '#.prototype', Object);
   var names = getOwnPropertyNames(coreObjProto);
   for (int i = 0; i < JS('int', '#.length', names); ++i) {
     var name = JS('', '#[#]', names, i);
     var desc = getOwnPropertyDescriptor(coreObjProto, name);
-    defineProperty(jsProto, getExtensionSymbol(name), desc);
+    defineProperty(jsProto, JS('', '#.#', dartx, name), desc);
   }
 }
 
 final _extensionMap = JS('', 'new Map()');
 
 _applyExtension(jsType, dartExtType) => JS('', '''(() => {
   // TODO(vsm): Not all registered js types are real.
   if (!$jsType) return;
 
   let jsProto = $jsType.prototype;
@@ skipping 51 matching lines @@
 ///     MyType.prototype[dartx.remove] = MyType.prototype.remove;
 ///
 // TODO(jmesserly): essentially this gives two names to the same method.
 // This benefit is roughly equivalent call performance either way, but the
 // cost is we need to call defineExtensionMembers any time a subclass
 // overrides one of these methods.
 defineExtensionMembers(type, methodNames) => JS('', '''(() => {
   let proto = $type.prototype;
   for (let name of $methodNames) {
     let method = $getOwnPropertyDescriptor(proto, name);
-    $defineProperty(proto, $getExtensionSymbol(name), method);
+    $defineProperty(proto, $dartx[name], method);
   }
   // Ensure the signature is available too.
   // TODO(jmesserly): not sure if we can do this in a cleaner way. Essentially
   // we need to copy the signature (and in the future, other data like
   // annotations) any time we copy a method as part of our metaprogramming.
   // It might be more friendly to JS metaprogramming if we include this info
   // on the function.
 
   function upgradeSig(sigF) {
     let originalSigDesc = $getOwnPropertyDescriptor($type, sigF);
     if (originalSigDesc === void 0) return;
     let originalSigFn = originalSigDesc.get;
     $defineMemoizedGetter(type, sigF, function() {
       let sig = originalSigFn();
       let propertyNames = Object.getOwnPropertyNames(sig);
       for (let name of methodNames) {
         if (name in sig) {
-          sig[$getExtensionSymbol(name)] = sig[name];
+          sig[$dartx[name]] = sig[name];
         }
       }
       return sig;
     });
   };
   upgradeSig($_methodSig);
   upgradeSig($_fieldSig);
   upgradeSig($_getterSig);
   upgradeSig($_setterSig);
 })()''');
@@ skipping 85 matching lines @@
 final isList = JS('', 'Symbol("_is_List")');
 
 /// The well known symbol for testing `is Map`
 final isMap = JS('', 'Symbol("_is_Map")');
 
 /// The well known symbol for testing `is Stream`
 final isStream = JS('', 'Symbol("_is_Stream")');
 
 /// The well known symbol for testing `is StreamSubscription`
 final isStreamSubscription = JS('', 'Symbol("_is_StreamSubscription")');