Hook in the version solver to pub install.

utils/pub/pubspec.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.
 
 #library('pubspec');
 
 #import('package.dart');
 #import('source.dart');
 #import('source_registry.dart');
 #import('utils.dart');
@@ skipping 42 matching lines @@
     if (parsedPubspec.containsKey('dependencies')) {
       var dependencyEntries = parsedPubspec['dependencies'];
       if (dependencyEntries is! Map ||
           dependencyEntries.getKeys().some((e) => e is! String)) {
         throw new FormatException(
             'The pubspec dependencies must be a map of package names.');
       }
 
       dependencyEntries.forEach((name, spec) {
         var description, source;
-        // TODO(nweiz): The correct default for versionConstraint is new
-        // VersionRange(), but that won't work until the version solver is
-        // hooked in.
-        var versionConstraint = Version.none;
+        var versionConstraint = new VersionRange();
         if (spec == null) {
           description = name;
           source = sources.defaultSource;
         } else if (spec is String) {
           description = name;
           source = sources.defaultSource;
           versionConstraint = new VersionConstraint.parse(spec);
         } else if (spec is Map) {
           if (spec.containsKey('version')) {
             versionConstraint = new VersionConstraint.parse(
@@ skipping 22 matching lines @@
         source.validateDescription(description);
 
         dependencies.add(new PackageRef(
             source, versionConstraint, description));
       });
     }
 
     return new Pubspec(version, dependencies);
   }
 }