Remove unneeded generation of default constructors from the dart backend.

sdk/lib/_internal/compiler/implementation/dart_backend/backend.dart

 // Copyright (c) 2012, 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.
 
 part of dart_backend;
 
 // TODO(ahe): This class is simply wrong.  This backend should use
 // elements when it can, not AST nodes.  Perhaps a [Map<Element,
 // TreeElements>] is what is needed.
 class ElementAst {
@@ skipping 328 matching lines @@
     usedTypeLiterals.forEach((ClassElement element) {
       if (shouldOutput(element)) {
         if (!topLevelElements.contains(element)) {
           // The class is only referenced by type literals.
           emitNoMembersFor.add(element);
         }
         addClass(element);
       }
     });
 
-    // Add synthesized constructors to classes with no resolved constructors,
-    // but which originally had any constructor.  That should prevent
-    // those classes from being instantiable with default constructor.
-    Identifier synthesizedIdentifier = new Identifier(
-        new StringToken.fromString(IDENTIFIER_INFO, '', -1));
-
-    NextClassElement:
-    for (ClassElement classElement in classMembers.keys) {
-      if (emitNoMembersFor.contains(classElement)) continue;
-      for (Element member in classMembers[classElement]) {
-        if (member.isConstructor) continue NextClassElement;
-      }
-      if (classElement.constructors.isEmpty) continue NextClassElement;
-
-      // TODO(antonm): check with AAR team if there is better approach.
-      // As an idea: provide template as a Dart code---class C { C.name(); }---
-      // and then overwrite necessary parts.
-      var classNode = classElement.node;
-      SynthesizedConstructorElementX constructor =
-          new SynthesizedConstructorElementX(
-              classElement.name, null, classElement, false);
-      constructor.typeCache =
-          new FunctionType(constructor, const VoidType());
-      if (!constructor.isSynthesized) {
-        classMembers[classElement].add(constructor);
-      }
-      FunctionExpression node = new FunctionExpression(
-          new Send(classNode.name, synthesizedIdentifier),
-          new NodeList(new StringToken.fromString(OPEN_PAREN_INFO, '(', -1),
-                       const Link<Node>(),
-                       new StringToken.fromString(CLOSE_PAREN_INFO, ')', -1)),
-          new EmptyStatement(
-              new StringToken.fromString(SEMICOLON_INFO, ';', -1)),
-          null, Modifiers.EMPTY, null, null);
-
-      elementAsts[constructor] =
-          new ElementAst.internal(node, new TreeElementMapping(null));
-    }
-
     // Create all necessary placeholders.
     PlaceholderCollector collector =
         new PlaceholderCollector(compiler, fixedMemberNames, elementAsts);
-    // Add synthesizedIdentifier to set of unresolved names to rename it to
-    // some unused identifier.
-    collector.unresolvedNodes.add(synthesizedIdentifier);
     makePlaceholders(element) {
       bool oldUseHelper = useMirrorHelperLibrary;
       useMirrorHelperLibrary = (useMirrorHelperLibrary
                                && element.library != mirrorHelperLibrary);
       collector.collect(element);
       useMirrorHelperLibrary = oldUseHelper;
 
       if (element.isClass) {
         classMembers[element].forEach(makePlaceholders);
       }
@@ skipping 377 matching lines @@
   }
 
   Constant compileMetadata(MetadataAnnotation metadata,
                            Node node,
                            TreeElements elements) {
     return measure(() {
       return constantCompiler.compileMetadata(metadata, node, elements);
     });
   }
 }