Rewrite how we handle synthesized constructors in the compiler. This was motivated by issue https:/…

sdk/lib/_internal/compiler/implementation/compiler.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 dart2js;
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
@@ skipping 1024 matching lines @@
     log('Excess resolution work: ${resolved.length}.');
     for (Element e in resolved) {
       SourceSpan span = spanFromElement(e);
       reportDiagnostic(span, 'Warning: $e resolved but not compiled.',
                        api.Diagnostic.WARNING);
     }
   }
 
   TreeElements analyzeElement(Element element) {
     assert(invariant(element, element.isDeclaration));
-    assert(!element.isForwardingConstructor);
     ResolutionEnqueuer world = enqueuer.resolution;
     TreeElements elements = world.getCachedElements(element);
     if (elements != null) return elements;
     assert(parser != null);
     Node tree = parser.parse(element);
-    validator.validate(tree);
+    assert(invariant(element, !element.isSynthesized || tree == null));
+    if (tree != null) validator.validate(tree);
     elements = resolver.resolve(element);
-    if (elements != null && !analyzeSignaturesOnly) {
+    if (tree != null && elements != null && !analyzeSignaturesOnly) {
       // Only analyze nodes with a corresponding [TreeElements].
       checker.check(elements);
     }
     world.resolvedElements[element] = elements;
     return elements;
   }
 
   TreeElements analyze(ResolutionWorkItem work, ResolutionEnqueuer world) {
     assert(invariant(work.element, identical(world, enqueuer.resolution)));
     assert(invariant(work.element, !work.isAnalyzed(),
@@ skipping 385 matching lines @@
 
   void close() {}
 
   toString() => name;
 
   /// Convenience method for getting an [api.CompilerOutputProvider].
   static NullSink outputProvider(String name, String extension) {
     return new NullSink('$name.$extension');
   }
 }