improve parser recovery for import directives

pkg/analyzer/test/generated/parser_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 engine.parser_test;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
@@ skipping 3251 matching lines @@
     NodeList<VariableDeclaration> vars =
         (fieldDecl as FieldDeclaration).fields.variables;
     expect(vars, hasLength(1));
     expect(vars[0].name.name, "v");
   }
 
   void test_functionExpression_named() {
     parseExpression("m(f() => 0);", [ParserErrorCode.EXPECTED_TOKEN]);
   }
 
+  void test_importDirectivePartial() {

[Brian Wilkerson, 2015/04/07 23:09:14]

Seems more common cases would be both
  "import 'b.dart' d"
and
  "import 'b.dart' d import"

[danrubel, 2015/04/08 15:39:22]

Good point. I'll add tests for those situations.

+    CompilationUnit unit = ParserTestCase.parseCompilationUnit(
+        "import 'b.dart' d as b;",
+        [ParserErrorCode.UNEXPECTED_TOKEN]);
+    ImportDirective importDirective = unit.childEntities.first;
+    expect(importDirective.asKeyword, isNotNull);
+    expect(unit.directives, hasLength(1));
+    expect(unit.declarations, hasLength(0));
+  }
+
   void test_incomplete_conditionalExpression() {
     parseExpression("x ? 0", [
       ParserErrorCode.EXPECTED_TOKEN,
       ParserErrorCode.MISSING_IDENTIFIER
     ]);
   }
 
   void test_incomplete_constructorInitializers_empty() {
     parse3("parseClassMember", ["C"], "C() : {}",
         [ParserErrorCode.MISSING_INITIALIZER]);
@@ skipping 6929 matching lines @@
         new Scanner(null, new CharSequenceReader(source), listener);
     Token tokenStream = scanner.tokenize();
     //
     // Parse the source.
     //
     Parser parser = new Parser(null, listener);
     return invokeParserMethodImpl(
         parser, methodName, <Object>[tokenStream], tokenStream) as Token;
   }
 }