Support for line-level error suppression (#25685).

pkg/analyzer/test/generated/resolver_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library analyzer.test.generated.resolver_test;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 13924 matching lines @@
     Source source = addSource(r'''
 class C {
   Iterable/*<T>*/ f/*<T>*/(/*=T*/ x) => null;
 }
 class D extends C {
   String f/*<S>*/(/*=S*/ x) => null;
 }''');
     // TODO(jmesserly): we can't use assertErrors because STRONG_MODE_* errors
     // from CodeChecker don't have working equality.
     List<AnalysisError> errors = analysisContext2.computeErrors(source);
+
+    // Sort errors by name.
+    errors.sort((AnalysisError e1, AnalysisError e2) =>
+        e1.errorCode.name.compareTo(e2.errorCode.name));
+
     expect(errors.map((e) => e.errorCode.name), [
       'INVALID_METHOD_OVERRIDE_RETURN_TYPE',
       'STRONG_MODE_INVALID_METHOD_OVERRIDE'
     ]);
     expect(errors[0].message, contains('Iterable<S>'),
         reason: 'errors should be in terms of the type parameters '
             'at the error location');
     verify([source]);
   }
 
@@ skipping 3168 matching lines @@
 
   void _resolveTestUnit(String code) {
     testCode = code;
     testSource = addSource(testCode);
     LibraryElement library = resolve2(testSource);
     assertNoErrors(testSource);
     verify([testSource]);
     testUnit = resolveCompilationUnit(testSource, library);
   }
 }