in pub build the analyzer prints errors but build succeeds and the result works fine
(with a newer analyzer 0.12.2 or 0.130-dev.x the build fails)

zoechi@znote_linux ~/source/my/dart/polymer_bugs/import_element_client
 (master) $ pub build
Building import_element_client...Build error:

Transform polymer (Linter) on import_element_client|web/index.html threw error: Could not find asset import_element_client|web/index.html.
package:barback/src/asset_node.dart 85       AssetNode.whenAvailable.<fn>
package:barback/src/asset_node.dart 115      AssetNode._waitForState.<fn>
dart:async                                   Future.Future.sync
package:barback/src/utils.dart 225           syncFuture
package:barback/src/asset_node.dart 115      AssetNode._waitForState
package:barback/src/asset_node.dart 83       AssetNode.whenAvailable
package:barback/src/transform_node.dart 180  TransformNode._apply
package:barback/src/transform_node.dart 107  TransformNode.TransformNode
package:barback/src/phase_input.dart 241     PhaseInput._addFreshTransforms.<fn>.<fn>
dart:isolate                                 _RawReceivePortImpl._handleMessage

Build error:
Transform polymer (Linter) on import_element_client|web/src/app_element/app_element.html threw error: Could not find asset import_element_client|web/src/app_element/app_element.html.
package:barback/src/asset_node.dart 85       AssetNode.whenAvailable.<fn>
package:barback/src/asset_node.dart 115      AssetNode._waitForState.<fn>
dart:async                                   Future.Future.sync
package:barback/src/utils.dart 225           syncFuture
package:barback/src/asset_node.dart 115      AssetNode._waitForState
package:barback/src/asset_node.dart 83       AssetNode.whenAvailable
package:barback/src/transform_node.dart 180  TransformNode._apply
package:barback/src/transform_node.dart 107  TransformNode.TransformNode
package:barback/src/phase_input.dart 241     PhaseInput._addFreshTransforms.<fn>.<fn>
dart:isolate                                 _RawReceivePortImpl._handleMessage

Build error:
Transform polymer (Linter) on import_element|lib/second_element/second_element.html threw error: Could not find asset import_element|lib/second_element/second_element.html.
package:barback/src/asset_node.dart 85       AssetNode.whenAvailable.<fn>
package:barback/src/asset_node.dart 115      AssetNode._waitForState.<fn>
dart:async                                   Future.Future.sync
package:barback/src/utils.dart 225           syncFuture
package:barback/src/asset_node.dart 115      AssetNode._waitForState
package:barback/src/asset_node.dart 83       AssetNode.whenAvailable
package:barback/src/transform_node.dart 180  TransformNode._apply
package:barback/src/transform_node.dart 107  TransformNode.TransformNode
package:barback/src/phase_input.dart 241     PhaseInput._addFreshTransforms.<fn>.<fn>
dart:isolate                                 _RawReceivePortImpl._handleMessage

Build error:
Transform polymer (Linter) on import_element|lib/first_element/first_element.html threw error: Could not find asset import_element|lib/first_element/first_element.html.
package:barback/src/asset_node.dart 85       AssetNode.whenAvailable.<fn>
package:barback/src/asset_node.dart 115      AssetNode._waitForState.<fn>
dart:async                                   Future.Future.sync
package:barback/src/utils.dart 225           syncFuture
package:barback/src/asset_node.dart 115      AssetNode._waitForState
package:barback/src/asset_node.dart 83       AssetNode.whenAvailable
package:barback/src/transform_node.dart 180  TransformNode._apply
package:barback/src/transform_node.dart 107  TransformNode.TransformNode
package:barback/src/phase_input.dart 241     PhaseInput._addFreshTransforms.<fn>.<fn>
dart:isolate                                 _RawReceivePortImpl._handleMessage

[Info from Dart2JS]:
Compiling import_element_client|web/src/app_element/app_element.dart...
[Info from Dart2JS]:
Compiling import_element_client|web/index.html.0.dart...
[Info from Dart2JS]:
Compiling import_element_client|web/index.html_bootstrap.dart...
[Warning from Dart2JS]:[Info from Dart2JS on import_element_client|web/index.html_bootstrap.dart]:

web/index.html_bootstrap.dart:packages/polymer/polymer.dart:50:1:

59 methods retained for use by dart:mirrors out of 2172 total methods (3%).Import of 'dart:mirrors'.

import 'dart:mirrors';
^^^^^^^^^^^^^^^^^^^^^^
[Info from Dart2JS on import_element_client|web/index.html_bootstrap.dart]:
packages/observe/src/observable.dart:16:1:
Import of 'dart:mirrors'.
import 'dart:mirrors';
^^^^^^^^^^^^^^^^^^^^^^
[Info from Dart2JS on import_element_client|web/index.html_bootstrap.dart]:
packages/observe/src/path_observer.dart:10:1:
Import of 'dart:mirrors'.
import 'dart:mirrors';
^^^^^^^^^^^^^^^^^^^^^^
[Info from Dart2JS on import_element_client|web/index.html_bootstrap.dart]:
packages/polymer_expressions/eval.dart:12:1:
Import of 'dart:mirrors'.
import 'dart:mirrors';
^^^^^^^^^^^^^^^^^^^^^^
[Info from Dart2JS on import_element_client|web/index.html_bootstrap.dart]:
packages/polymer_expressions/src/mirrors.dart:11:1:
Import of 'dart:mirrors'.
import 'dart:mirrors';
^^^^^^^^^^^^^^^^^^^^^^
[Info from Dart2JS on import_element_client|web/index.html_bootstrap.dart]:
packages/polymer/deserialize.dart:8:1:
Import of 'dart:mirrors'.
import 'dart:mirrors' show TypeMirror;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[Info from Dart2JS]:
Took 0:00:24.570026 to compile import_element_client|web/index.html_bootstrap.dart.
Built 26 files!