Issue 25733. Built-in itentifiers are not permitted as prefixes.

pkg/analyzer/test/generated/compile_time_error_code_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.compile_time_error_code_test;
 
 import 'dart:async';
 
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/src/error/codes.dart';
@@ skipping 606 matching lines @@
     Source source = addSource(r'''
 class A {}
 class B {}
 class as = A with B;''');
     await computeAnalysisResult(source);
     assertErrors(
         source, [CompileTimeErrorCode.BUILT_IN_IDENTIFIER_AS_TYPEDEF_NAME]);
     verify([source]);
   }
 
+  test_builtInIdentifierAsPrefixName() async {
+    Source source = addSource("import 'dart:async' as abstract;");
+    await computeAnalysisResult(source);
+    assertErrors(source, [
+      CompileTimeErrorCode.BUILT_IN_IDENTIFIER_AS_PREFIX_NAME,
+      HintCode.UNUSED_IMPORT
+    ]);
+    verify([source]);
+  }
+
   test_builtInIdentifierAsType_formalParameter_field() async {
     Source source = addSource(r'''
 class A {
   var x;
   A(static this.x);
 }''');
     await computeAnalysisResult(source);
     assertErrors(source, [CompileTimeErrorCode.BUILT_IN_IDENTIFIER_AS_TYPE]);
     verify([source]);
   }
@@ skipping 5852 matching lines @@
         source, [CompileTimeErrorCode.WRONG_NUMBER_OF_PARAMETERS_FOR_OPERATOR]);
     verify([source]);
     reset();
   }
 
   Future<Null> _check_wrongNumberOfParametersForOperator1(String name) async {
     await _check_wrongNumberOfParametersForOperator(name, "");
     await _check_wrongNumberOfParametersForOperator(name, "a, b");
   }
 }