Error reporting for spans.

R=brianwilkerson@google.com, scheglov@google.com

Review URL: https://codereview.chromium.org/1418973002 .

(cherry picked from commit 0881b53)

Author: pq

Diff for: pkg/analyzer/lib/src/generated/error.dart

@@ -6,6 +6,8 @@ library engine.error;
 
 import 'dart:collection';
 
+import 'package:source_span/source_span.dart';
+
 import 'ast.dart' show AstNode;
 import 'element.dart';
 import 'java_core.dart';
@@ -2662,6 +2664,15 @@ class ErrorReporter {
         new AnalysisError(_source, offset, length, errorCode, arguments));
   }
 
+  /**
+   * Report an error with the given [errorCode] and [arguments]. The location of
+   * the error is specified by the given [span].
+   */
+  void reportErrorForSpan(ErrorCode errorCode, SourceSpan span,
+      [List<Object> arguments]) {
+    reportErrorForOffset(errorCode, span.start.offset, span.length, arguments);
+  }
+
   /**
    * Report an error with the given [errorCode] and [arguments]. The [token] is
    * used to compute the location of the error.

Diff for: pkg/analyzer/test/generated/all_the_rest_test.dart

@@ -30,6 +30,7 @@ import 'package:analyzer/src/generated/utilities_collection.dart';
 import 'package:analyzer/src/generated/utilities_dart.dart';
 import 'package:analyzer/src/task/dart.dart';
 import 'package:path/path.dart';
+import 'package:source_span/source_span.dart';
 import 'package:unittest/unittest.dart';
 
 import '../reflective_tests.dart';
@@ -7334,6 +7335,27 @@ class ErrorReporterTest extends EngineTestCase {
     expect(error.offset, element.nameOffset);
   }
 
+  void test_reportErrorForSpan() {
+    GatheringErrorListener listener = new GatheringErrorListener();
+    ErrorReporter reporter = new ErrorReporter(listener, new TestSource());
+
+    var src = '''
+foo: bar
+zap: baz
+''';
+
+    int offset = src.indexOf('baz');
+    int length = 'baz'.length;
+
+    SourceSpan span = new SourceFile(src).span(offset, offset + length);
+
+    reporter.reportErrorForSpan(
+        AnalysisOptionsWarningCode.UNSUPPORTED_OPTION, span, ['test', 'zap']);
+    expect(listener.errors, hasLength(1));
+    expect(listener.errors.first.offset, offset);
+    expect(listener.errors.first.length, length);
+  }
+
   void test_reportTypeErrorForNode_differentNames() {
     DartType firstType = createType("/test1.dart", "A");
     DartType secondType = createType("/test2.dart", "B");