Improve strong-mode implementation and fix several failing tests

pkg/analyzer/lib/src/generated/engine.dart

Index: pkg/analyzer/lib/src/generated/engine.dart
diff --git a/pkg/analyzer/lib/src/generated/engine.dart b/pkg/analyzer/lib/src/generated/engine.dart
index 5eccbf7ee5b33c7932856815551ae5e221f02f47..80b2ad660c9136d9ce24d89d8fa77589af93eeff 100644
--- a/pkg/analyzer/lib/src/generated/engine.dart
+++ b/pkg/analyzer/lib/src/generated/engine.dart
@@ -8415,6 +8415,62 @@ class DefaultRetentionPolicy implements CacheRetentionPolicy {
 }
 
 /**
+ * An error listener that can be enabled or disabled while executing a function.
+ */
+class DisablableErrorListener implements AnalysisErrorListener {

[scheglov, 2015/09/08 15:36:22]

Why don't we put it in error.dart ?

[Brian Wilkerson, 2015/09/08 17:10:33]

Done

+  /**
+   * The listener to which errors will be reported if this listener is enabled.
+   */
+  final AnalysisErrorListener baseListener;
+
+  /**
+   * A flag indicating whether this listener is currently enabled.
+   */
+  bool enabled = true;
+
+  /**
+   * Initialize a newly created listener to report errors to the given
+   * [baseListener].
+   */
+  DisablableErrorListener(this.baseListener);
+
+  /**
+   * Disable the processing of errors while evaluating the given [function].
+   * Return the value returned by the function.
+   */
+  dynamic disableWhile(dynamic function()) {
+    bool wasEnabled = enabled;
+    try {
+      enabled = false;
+      return function();
+    } finally {
+      enabled = wasEnabled;
+    }
+  }
+
+  /**
+   * Disable the processing of errors while evaluating the given [function].
+   * Return the value returned by the function.
+   */
+  dynamic enableWhile(dynamic function()) {
+    bool wasEnabled = enabled;
+    try {
+      enabled = true;
+      return function();
+    } finally {
+      enabled = wasEnabled;
+    }
+  }
+
+  @override
+  void onError(AnalysisError error) {
+    if (enabled) {
+      baseListener.onError(error);
+    }
+  }
+}
+
+/**
  * Instances of the class `GenerateDartErrorsTask` generate errors and warnings for a single
  * Dart source.
  */