fix unterminated interpolation expression handling

pkg/front_end/test/scanner_fasta_test.dart

 // Copyright (c) 2017, 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 'dart:convert';
 
 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;
@@ skipping 311 matching lines @@
     expect((token as fasta.ErrorToken).errorCode, same(codeUnmatchedToken));
     expect((token as fasta.UnmatchedToken).begin, same(interpolationStart));
 
     token = token.next;
     expectToken(token, TokenType.STRING, 10, 0, isSynthetic: true, lexeme: '"');
 
     token = token.next;
     expect((token as fasta.ErrorToken).errorCode, same(codeUnterminatedString));
   }
 
+  void test_string_simple_unterminated_interpolation_block2() {
+    Token token = scan(r'"foo ${bar(baz[');
+    expectToken(token, TokenType.STRING, 0, 5, lexeme: '"foo ');
+
+    token = token.next;
+    expectToken(token, TokenType.STRING_INTERPOLATION_EXPRESSION, 5, 2);
+    BeginToken interpolationStart = token;
+
+    token = token.next;
+    expectToken(token, TokenType.IDENTIFIER, 7, 3, lexeme: 'bar');
+
+    token = token.next;
+    expectToken(token, TokenType.OPEN_PAREN, 10, 1);
+    BeginToken openParen = token;
+
+    token = token.next;
+    expectToken(token, TokenType.IDENTIFIER, 11, 3, lexeme: 'baz');
+
+    token = token.next;
+    expectToken(token, TokenType.OPEN_SQUARE_BRACKET, 14, 1);
+    BeginToken openSquareBracket = token;
+
+    token = token.next;
+    expectToken(token, TokenType.CLOSE_SQUARE_BRACKET, 15, 0,
+        isSynthetic: true, lexeme: ']');
+    expect(openSquareBracket.endToken, same(token));
+
+    token = token.next;
+    expect((token as fasta.ErrorToken).errorCode, same(codeUnmatchedToken));
+    expect((token as fasta.UnmatchedToken).begin, same(openSquareBracket));
+
+    token = token.next;
+    expectToken(token, TokenType.CLOSE_PAREN, 15, 0,
+        isSynthetic: true, lexeme: ')');
+    expect(openParen.endToken, same(token));
+
+    token = token.next;
+    expect((token as fasta.ErrorToken).errorCode, same(codeUnmatchedToken));
+    expect((token as fasta.UnmatchedToken).begin, same(openParen));
+
+    token = token.next;
+    expectToken(token, TokenType.CLOSE_CURLY_BRACKET, 15, 0,
+        isSynthetic: true, lexeme: '}');
+    expect(interpolationStart.endToken, same(token));
+
+    token = token.next;
+    expect((token as fasta.ErrorToken).errorCode, same(codeUnmatchedToken));
+    expect((token as fasta.UnmatchedToken).begin, same(interpolationStart));
+
+    token = token.next;
+    expectToken(token, TokenType.STRING, 15, 0, isSynthetic: true, lexeme: '"');
+
+    token = token.next;
+    expect((token as fasta.ErrorToken).errorCode, same(codeUnterminatedString));
+  }
+
   void test_string_simple_missing_interpolation_identifier() {
     Token token = scan(r'"foo $');
     expectToken(token, TokenType.STRING, 0, 5, lexeme: '"foo ');
 
     token = token.next;
     expectToken(token, TokenType.STRING_INTERPOLATION_IDENTIFIER, 5, 1);
 
     token = token.next;
     expect((token as fasta.ErrorToken).errorCode,
         same(codeUnexpectedDollarInString));
@@ skipping 268 matching lines @@
   final ErrorListener _listener;
 
   ToAnalyzerTokenStreamConverter_WithListener(this._listener);
 
   @override
   void reportError(
       ScannerErrorCode errorCode, int offset, List<Object> arguments) {
     _listener.errors.add(new TestError(offset, errorCode, arguments));
   }
 }