Synthesized a constructor if there is no resolved constructors in the class.

lib/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.
 
 const bool REMOVE_ASSERTS = false;
 
 class ElementAst {
   final Node ast;
   final TreeElements treeElements;
 
@@ skipping 311 matching lines @@
         classMembers[enclosingClass].add(element);
         processElement(element, elementAst);
       } else {
         if (!element.isTopLevel()) {
           compiler.cancel(reason: 'Cannot process $element', element: element);
         }
         addTopLevel(element, elementAst);
       }
     });
 
+    // 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(IDENTIFIER_INFO, '', -1));
+
+    NextClassElement:
+    for (ClassElement classElement in classMembers.getKeys()) {
+      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.
+      SynthesizedConstructorElement constructor =
+          new SynthesizedConstructorElement(classElement);
+      constructor.type = new FunctionType(
+          compiler.types.voidType, const EmptyLink<DartType>(),
+          constructor);
+      constructor.cachedNode = new FunctionExpression(
+          new Send(receiver: classElement.parseNode(compiler).name,
+                   selector: synthesizedIdentifier),
+          new NodeList(beginToken: new StringToken(OPEN_PAREN_INFO, '(', -1),
+                       endToken: new StringToken(CLOSE_PAREN_INFO, ')', -1),
+                       nodes: const EmptyLink<Node>()),
+          new EmptyStatement(new StringToken(SEMICOLON_INFO, ';', -1)),
+          null, null, null, null);
+
+      classMembers[classElement].add(constructor);
+      elementAsts[constructor] =
+          new ElementAst(constructor.cachedNode, new TreeElementMapping());
+    }
+
     // 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) {
       collector.collect(element);
       if (element is ClassElement) {
         classMembers[element].forEach(makePlaceholders);
       }
     }
     topLevelElements.forEach(makePlaceholders);
     // Create renames.
     Map<Node, String> renames = new Map<Node, String>();
     Map<LibraryElement, String> imports = new Map<LibraryElement, String>();
@@ skipping 110 matching lines @@
 }
 
 compareElements(e0, e1) {
   int result = compareBy((e) => e.getLibrary().uri.toString())(e0, e1);
   if (result != 0) return result;
   return compareBy((e) => e.position().charOffset)(e0, e1);
 }
 
 List<Element> sortElements(Collection<Element> elements) =>
     sorted(elements, compareElements);