Create a NullErrorReporter to use when errors don't need to be recorded.

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

Index: pkg/analyzer/lib/src/generated/error.dart
diff --git a/pkg/analyzer/lib/src/generated/error.dart b/pkg/analyzer/lib/src/generated/error.dart
index 1d5beba66fd7413f8b91e4e210c83b7cb032f8de..6ce7696b77758e72867dac9c0c17afbae8fe61ce 100644
--- a/pkg/analyzer/lib/src/generated/error.dart
+++ b/pkg/analyzer/lib/src/generated/error.dart
@@ -2120,38 +2120,11 @@ class ErrorProperty extends Enum<ErrorProperty> {
  * Instances of the class `ErrorReporter` wrap an error listener with utility methods used to
  * create the errors being reported.
  */
-class ErrorReporter {
+abstract class ErrorReporter {

[Brian Wilkerson, 2014/10/06 14:10:08]

I'm not sure why we needed to make this an abstract class. NullErrorReporter
could have implemented the original definition.

[Paul Berry, 2014/10/06 16:44:39]

Since NullErrorReporter is in the same library as ErrorReporter, it would also
have to have implemented ErrorReporter._hasEqualTypeNames,
ErrorReporter._errorListener, and ErrorReporter._convertTypeNames.  I suppose I
could have just left these methods empty, but that seemed clumsy.

Guess it's a moot point now, though :)

   /**
-   * The error listener to which errors will be reported.
-   */
-  final AnalysisErrorListener _errorListener;
-
-  /**
-   * The default source to be used when reporting errors.
-   */
-  final Source _defaultSource;
-
-  /**
-   * The source to be used when reporting errors.
+   * The source used when reporting errors.
    */
-  Source _source;
-
-  /**
-   * Initialize a newly created error reporter that will report errors to the given listener.
-   *
-   * @param errorListener the error listener to which errors will be reported
-   * @param defaultSource the default source to be used when reporting errors
-   */
-  ErrorReporter(this._errorListener, this._defaultSource) {
-    if (_errorListener == null) {
-      throw new IllegalArgumentException("An error listener must be provided");
-    } else if (_defaultSource == null) {
-      throw new IllegalArgumentException("A default source must be provided");
-    }
-    this._source = _defaultSource;
-  }
-
-  Source get source => _source;
+  Source get source;
 
   /**
    * Creates an error with properties with the given error code and arguments.
@@ -2160,16 +2133,14 @@ class ErrorReporter {
    * @param node the node specifying the location of the error
    * @param arguments the arguments to the error, used to compose the error message
    */
-  AnalysisErrorWithProperties newErrorWithProperties(ErrorCode errorCode, AstNode node, List<Object> arguments) => new AnalysisErrorWithProperties.con2(_source, node.offset, node.length, errorCode, arguments);
+  AnalysisErrorWithProperties newErrorWithProperties(ErrorCode errorCode, AstNode node, List<Object> arguments);
 
   /**
    * Report a passed error.
    *
    * @param error the error to report
    */
-  void reportError(AnalysisError error) {
-    _errorListener.onError(error);
-  }
+  void reportError(AnalysisError error);
 
   /**
    * Report an error with the given error code and arguments.
@@ -2178,9 +2149,7 @@ class ErrorReporter {
    * @param element the element which name should be used as the location of the error
    * @param arguments the arguments to the error, used to compose the error message
    */
-  void reportErrorForElement(ErrorCode errorCode, Element element, List<Object> arguments) {
-    reportErrorForOffset(errorCode, element.nameOffset, element.displayName.length, arguments);
-  }
+  void reportErrorForElement(ErrorCode errorCode, Element element, List<Object> arguments);
 
   /**
    * Report an error with the given error code and arguments.
@@ -2193,9 +2162,7 @@ class ErrorReporter {
    * @param node the node specifying the location of the error
    * @param arguments the arguments to the error, used to compose the error message
    */
-  void reportErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments) {
-    reportErrorForOffset(errorCode, node.offset, node.length, arguments);
-  }
+  void reportErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments);
 
   /**
    * Report an error with the given error code and arguments.
@@ -2205,9 +2172,7 @@ class ErrorReporter {
    * @param length the length of the location of the error
    * @param arguments the arguments to the error, used to compose the error message
    */
-  void reportErrorForOffset(ErrorCode errorCode, int offset, int length, List<Object> arguments) {
-    _errorListener.onError(new AnalysisError.con2(_source, offset, length, errorCode, arguments));
-  }
+  void reportErrorForOffset(ErrorCode errorCode, int offset, int length, List<Object> arguments);
 
   /**
    * Report an error with the given error code and arguments.
@@ -2216,9 +2181,7 @@ class ErrorReporter {
    * @param token the token specifying the location of the error
    * @param arguments the arguments to the error, used to compose the error message
    */
-  void reportErrorForToken(ErrorCode errorCode, Token token, List<Object> arguments) {
-    reportErrorForOffset(errorCode, token.offset, token.length, arguments);
-  }
+  void reportErrorForToken(ErrorCode errorCode, Token token, List<Object> arguments);
 
   /**
    * Report an error with the given error code and arguments. The arguments are expected to contain
@@ -2233,10 +2196,7 @@ class ErrorReporter {
    * @param node the node specifying the location of the error
    * @param arguments the arguments to the error, used to compose the error message
    */
-  void reportTypeErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments) {
-    _convertTypeNames(arguments);
-    reportErrorForOffset(errorCode, node.offset, node.length, arguments);
-  }
+  void reportTypeErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments);
 
   /**
    * Set the source to be used when reporting errors. Setting the source to `null` will cause
@@ -2244,6 +2204,78 @@ class ErrorReporter {
    *
    * @param source the source to be used when reporting errors
    */
+  void set source(Source source);
+}
+
+class ErrorReporterImpl implements ErrorReporter {
+  /**
+   * The error listener to which errors will be reported.
+   */
+  final AnalysisErrorListener _errorListener;
+
+  /**
+   * The default source to be used when reporting errors.
+   */
+  final Source _defaultSource;
+
+  /**
+   * The source to be used when reporting errors.
+   */
+  Source _source;
+
+  /**
+   * Initialize a newly created error reporter that will report errors to the given listener.
+   *
+   * @param errorListener the error listener to which errors will be reported
+   * @param defaultSource the default source to be used when reporting errors
+   */
+  ErrorReporterImpl(this._errorListener, this._defaultSource) {
+    if (_errorListener == null) {
+      throw new IllegalArgumentException("An error listener must be provided");
+    } else if (_defaultSource == null) {
+      throw new IllegalArgumentException("A default source must be provided");
+    }
+    this._source = _defaultSource;
+  }
+
+  @override
+  Source get source => _source;
+
+  @override
+  AnalysisErrorWithProperties newErrorWithProperties(ErrorCode errorCode, AstNode node, List<Object> arguments) => new AnalysisErrorWithProperties.con2(_source, node.offset, node.length, errorCode, arguments);
+
+  @override
+  void reportError(AnalysisError error) {
+    _errorListener.onError(error);
+  }
+
+  @override
+  void reportErrorForElement(ErrorCode errorCode, Element element, List<Object> arguments) {
+    reportErrorForOffset(errorCode, element.nameOffset, element.displayName.length, arguments);
+  }
+
+  @override
+  void reportErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments) {
+    reportErrorForOffset(errorCode, node.offset, node.length, arguments);
+  }
+
+  @override
+  void reportErrorForOffset(ErrorCode errorCode, int offset, int length, List<Object> arguments) {
+    _errorListener.onError(new AnalysisError.con2(_source, offset, length, errorCode, arguments));
+  }
+
+  @override
+  void reportErrorForToken(ErrorCode errorCode, Token token, List<Object> arguments) {
+    reportErrorForOffset(errorCode, token.offset, token.length, arguments);
+  }
+
+  @override
+  void reportTypeErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments) {
+    _convertTypeNames(arguments);
+    reportErrorForOffset(errorCode, node.offset, node.length, arguments);
+  }
+
+  @override
   void set source(Source source) {
     this._source = source == null ? _defaultSource : source;
   }
@@ -2774,6 +2806,65 @@ class HtmlWarningCode extends Enum<HtmlWarningCode> implements ErrorCode {
   String get uniqueName => "${runtimeType.toString()}.${name}";
 }
 
+
+/**
+ * The class [NullErrorReporter] presents the same interface as [ErrorReporter]
+ * but discards all error information.
+ */
+class NullErrorReporter implements ErrorReporter {
+  /**
+   * The default source to be used when reporting errors.
+   */
+  final Source _defaultSource;
+
+  /**
+   * The source to be used when reporting errors.
+   */
+  Source _source;
+
+  NullErrorReporter(this._defaultSource) {
+    _source = _defaultSource;
+  }
+
+  @override
+  AnalysisErrorWithProperties newErrorWithProperties(ErrorCode errorCode, AstNode node, List<Object> arguments) {
+    return new AnalysisErrorWithProperties.con2(_source, node.offset, node.length, errorCode, arguments);
+  }
+
+  @override
+  void reportError(AnalysisError error) {
+  }
+
+  @override
+  void reportErrorForElement(ErrorCode errorCode, Element element, List<Object> arguments) {
+  }
+
+  @override
+  void reportErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments) {
+  }
+
+  @override
+  void reportErrorForOffset(ErrorCode errorCode, int offset, int length, List<Object> arguments) {
+  }
+
+  @override
+  void reportErrorForToken(ErrorCode errorCode, Token token, List<Object> arguments) {
+  }
+
+  @override
+  void reportTypeErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments) {
+  }
+
+  @override
+  void set source(Source source) {
+    this._source = source == null ? _defaultSource : source;
+  }
+
+  @override
+  Source get source => _source;
+}
+
+
 /**
  * The enumeration `PolymerCode` defines Polymer specific problems.
  */