improve fasta interpolation recovery

pkg/front_end/test/scanner_fasta_test.dart

Index: pkg/front_end/test/scanner_fasta_test.dart
diff --git a/pkg/front_end/test/scanner_fasta_test.dart b/pkg/front_end/test/scanner_fasta_test.dart
index 9e7564def0dc2cb6ed504681b4cd3c568d0965fe..f6b8cc1cacb3ff7144907705bfae43abdc31e21a 100644
--- a/pkg/front_end/test/scanner_fasta_test.dart
+++ b/pkg/front_end/test/scanner_fasta_test.dart
@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer/src/fasta/token_utils.dart';
+import 'package:front_end/src/fasta/fasta_codes.dart';
 import 'package:front_end/src/fasta/scanner/error_token.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/string_scanner.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/token.dart' as fasta;
@@ -23,6 +24,10 @@ main() {
 
 @reflectiveTest
 class ScannerTest_Fasta extends ScannerTestBase {
+  ScannerTest_Fasta() {
+    usingFasta = true;
+  }
+
   @override
   Token scanWithListener(String source, ErrorListener listener,
       {bool genericMethodComments: false,
@@ -179,14 +184,6 @@ main() {}
 
   @override
   @failingTest
-  void test_incomplete_string_interpolation() {
-    // TODO(danrubel): fix ToAnalyzerTokenStreamConverter_WithListener
-    // to handle synthetic closers in token stream
-    super.test_incomplete_string_interpolation();
-  }
-
-  @override
-  @failingTest
   void test_mismatched_closer() {
     // TODO(paulberry,ahe): Fasta and analyzer recover this error differently.
     // Figure out which recovery technique we want the front end to use.
@@ -503,6 +500,32 @@ class ScannerTest_Fasta_Direct extends ScannerTest_Fasta_Base {
     var scanner = new fasta.StringScanner(source, includeComments: true);
     return scanner.tokenize();
   }
+
+  test_unterminated_string_with_unterminated_interpolation() {
+    Token token = scan(r'"foo ${bar');
+    BeginToken interpolationStart = token.next;
+
+    Token previous;
+    while (token.kind != fasta.BAD_INPUT_TOKEN) {
+      expect(token.isEof, isFalse);
+      previous = token;
+      token = token.next;
+    }
+
+    // Expect interpolation to be terminated before string is closed
+
+    token = previous;
+    expect(token.isSynthetic, isTrue);
+    expect(token.length, 0);
+    expect(token.stringValue, '}');
+
+    token = token.next;
+    expect((token as fasta.ErrorToken).errorCode, same(codeUnmatchedToken));
+    expect((token as fasta.UnmatchedToken).begin, same(interpolationStart));
+
+    token = token.next;
+    expect((token as fasta.ErrorToken).errorCode, same(codeUnterminatedString));
+  }
 }
 
 /// Override of [ToAnalyzerTokenStreamConverter] that verifies that there are no