Travis CI failure due to Dart 2.1

[wing328]

Description

Travis CI failure due to installation of Dart 2.1 (released last week)

file:///home/travis/.pub-cache/hosted/pub.dartlang.org/front_end-0.1.4/lib/src/fasta/kernel/expression_generator.dart:740:14: Error: The method 'ErroneousExpressionGenerator::buildCompoundAssignment' doesn't have the named parameter 'isPostIncDec' of overridden method 'KernelExpressionGenerator::buildCompoundAssignment'.
  Expression buildCompoundAssignment(Name binaryOperator, Expression value,
             ^
file:///home/travis/.pub-cache/hosted/pub.dartlang.org/front_end-0.1.4/lib/src/fasta/kernel/kernel_expression_generator.dart:177:14: Context: This is the overridden method ('buildCompoundAssignment').
  Expression buildCompoundAssignment(Name binaryOperator, Expression value,
             ^
file:///home/travis/.pub-cache/hosted/pub.dartlang.org/front_end-0.1.4/lib/src/fasta/kernel/kernel_expression_generator.dart:1424:7: Context: Override was introduced when the mixin 'ErroneousExpressionGenerator' was applied to 'KernelGenerator'.
class KernelUnresolvedNameGenerator extends KernelGenerator
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
file:///home/travis/.pub-cache/hosted/pub.dartlang.org/front_end-0.1.4/lib/src/fasta/kernel/expression_generator.dart:894:14: Error: The method 'ContextAwareGenerator::buildCompoundAssignment' has fewer named arguments than those of overridden method 'KernelExpressionGenerator::buildCompoundAssignment'.
  Expression buildCompoundAssignment(Name binaryOperator, Expression value,
             ^
file:///home/travis/.pub-cache/hosted/pub.dartlang.org/front_end-0.1.4/lib/src/fasta/kernel/kernel_expression_generator.dart:177:14: Context: This is the overridden method ('buildCompoundAssignment').
  Expression buildCompoundAssignment(Name binaryOperator, Expression value,
             ^
file:///home/travis/.pub-cache/hosted/pub.dartlang.org/front_end-0.1.4/lib/src/fasta/kernel/kernel_expression_generator.dart:1513:16: Context: Override was introduced when the mixin 'ContextAwareGenerator' was applied to 'KernelGenerator'.
abstract class KernelContextAwareGenerator extends KernelGenerator
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^
file:///home/travis/.pub-cache/hosted/pub.dartlang.org/front_end-0.1.4/lib/src/fasta/kernel/expression_generator.dart:894:14: Error: The method 'ContextAwareGenerator::buildCompoundAssignment' doesn't have the named parameter 'isPostIncDec' of overridden method 'KernelExpressionGenerator::buildCompoundAssignment'.
  Expression buildCompoundAssignment(Name binaryOperator, Expression value,
             ^

Full log: https://travis-ci.org/OpenAPITools/openapi-generator/builds/455965775

The failure is caused by testing samples/client/petstore/dart2/petstore/ with Dart 2.1

openapi-generator version

Latest master

Suggest a fix/enhancement

The test for Dart2PetstoreClientTests has been commented out for the time being

cc @ircecho (2017/07) @swipesight (2018/09) @jaumard (2018/09)

[bigkrp]

Same issue

[wing328]

@bigkrp the issue should be fixed. Please try the latest stable version or master.