Make mappedBy lazy.

utils/pub/version.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.
 
 /**
  * Handles version numbers, following the [Semantic Versioning][semver] spec.
  *
  * [semver]: http://semver.org/
  */
 library version;
@@ skipping 169 matching lines @@
    * Identifiers that are numeric are converted to numbers.
    */
   List _splitParts(String text) {
     return text.split('.').mappedBy((part) {
       try {
         return int.parse(part);
       } on FormatException catch (ex) {
         // Not a number.
         return part;
       }
-    });
+    }).toList();
   }
 }
 
 /**
  * A [VersionConstraint] is a predicate that can determine whether a given
  * version is valid or not. For example, a ">= 2.0.0" constraint allows any
  * version that is "2.0.0" or greater. Version objects themselves implement
  * this to match a specific version.
  */
 interface VersionConstraint default _VersionConstraintFactory {
@@ skipping 18 matching lines @@
    *     >2.0.4 <=2.4.6
    */
   VersionConstraint.parse(String text);
 
   /**
    * Creates a new version constraint that is the intersection of [constraints].
    * It will only allow versions that all of those constraints allow. If
    * constraints is empty, then it returns a VersionConstraint that allows all
    * versions.
    */
-  VersionConstraint.intersect(Collection<VersionConstraint> constraints);
+  VersionConstraint.intersect(Iterable<VersionConstraint> constraints);
 
   /**
    * Returns `true` if this constraint allows no versions.
    */
   bool get isEmpty;
 
   /**
    * Returns `true` if this constraint allows [version].
    */
   bool allows(Version version);
@@ skipping 146 matching lines @@
     // Split it into space-separated parts.
     var constraints = <VersionConstraint>[];
     for (var part in text.split(' ')) {
       constraints.add(parseSingleConstraint(part));
     }
 
     return new VersionConstraint.intersect(constraints);
   }
 
   factory VersionConstraint.intersect(
-      Collection<VersionConstraint> constraints) {
+      Iterable<VersionConstraint> constraints) {
     var constraint = new VersionRange();
     for (var other in constraints) {
       constraint = constraint.intersect(other);
     }
     return constraint;
   }
 
   static VersionConstraint parseSingleConstraint(String text) {
     if (text == 'any') {
       return new VersionRange();
@@ skipping 13 matching lines @@
         case '<': return new VersionRange(max: version, includeMax: false);
         case '>=': return new VersionRange(min: version, includeMin: true);
         case '>': return new VersionRange(min: version, includeMin: false);
       }
     }
 
     // Otherwise, it must be an explicit version.
     return new Version.parse(text);
   }
 }