improve fasta interpolation recovery

pkg/front_end/test/scanner_test.dart

 // Copyright (c) 2016, 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.
 
 import 'package:front_end/src/base/errors.dart';
 import 'package:front_end/src/base/jenkins_smi_hash.dart';
 import 'package:front_end/src/scanner/errors.dart';
 import 'package:front_end/src/scanner/reader.dart';
 import 'package:front_end/src/scanner/scanner.dart';
 import 'package:front_end/src/scanner/token.dart';
@@ skipping 118 matching lines @@
   @override
   Token scanWithListener(String source, ErrorListener listener,
       {bool genericMethodComments: false,
       bool lazyAssignmentOperators: false}) {
     Scanner scanner =
         new _TestScanner(new CharSequenceReader(source), listener);
     scanner.scanGenericMethodComments = genericMethodComments;
     scanner.scanLazyAssignmentOperators = lazyAssignmentOperators;
     return scanner.tokenize();
   }
-
-  @override
-  @failingTest
-  void test_incomplete_string_interpolation() {
-    super.test_incomplete_string_interpolation();
-  }
 }
 
 abstract class ScannerTestBase {
+  bool usingFasta = false;
+
   Token scanWithListener(String source, ErrorListener listener,
       {bool genericMethodComments: false, bool lazyAssignmentOperators: false});
 
   void test_ampersand() {
     _assertToken(TokenType.AMPERSAND, "&");
   }
 
   void test_ampersand_ampersand() {
     _assertToken(TokenType.AMPERSAND_AMPERSAND, "&&");
   }
@@ skipping 269 matching lines @@
   void test_illegalChar_nbsp() {
     _assertError(ScannerErrorCode.ILLEGAL_CHARACTER, 0, "\u00A0", [0xa0]);
   }
 
   void test_illegalChar_notLetter() {
     _assertError(ScannerErrorCode.ILLEGAL_CHARACTER, 0, "\u0312", [0x312]);
   }
 
   void test_incomplete_string_interpolation() {
     // https://code.google.com/p/dart/issues/detail?id=18073
-    _assertErrorAndTokens(
-        ScannerErrorCode.UNTERMINATED_STRING_LITERAL, 9, "\"foo \${bar", [
+    List<Token> expectedTokens = [
       new StringToken(TokenType.STRING, "\"foo ", 0),
       new StringToken(TokenType.STRING_INTERPOLATION_EXPRESSION, "\${", 5),
-      new StringToken(TokenType.IDENTIFIER, "bar", 7)
-    ]);
+      new StringToken(TokenType.IDENTIFIER, "bar", 7),
+    ];
+    if (usingFasta) {
+      // fasta inserts synthetic closers
+      expectedTokens.addAll([
+        new SyntheticToken(TokenType.CLOSE_CURLY_BRACKET, 10),
+      ]);
+    } else {
+      expectedTokens.addAll([
+        new StringToken(TokenType.STRING, "", 10),
+      ]);
+    }
+    _assertErrorAndTokens(ScannerErrorCode.UNTERMINATED_STRING_LITERAL, 9,
+        "\"foo \${bar", expectedTokens);
   }
 
   void test_index() {
     _assertToken(TokenType.INDEX, "[]");
   }
 
   void test_index_eq() {
     _assertToken(TokenType.INDEX_EQ, "[]=");
   }
 
@@ skipping 1046 matching lines @@
   _TestScanner(CharacterReader reader, [this.listener]) : super.create(reader);
 
   @override
   void reportError(
       ScannerErrorCode errorCode, int offset, List<Object> arguments) {
     if (listener != null) {
       listener.errors.add(new TestError(offset, errorCode, arguments));
     }
   }
 }