improve fasta unterminated string 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 f6b8cc1cacb3ff7144907705bfae43abdc31e21a..61848f26b2fa8b746f001b84aa68f6eb590d23ab 100644
--- a/pkg/front_end/test/scanner_fasta_test.dart
+++ b/pkg/front_end/test/scanner_fasta_test.dart
@@ -241,13 +241,6 @@ main() {}
 
   @override
   @failingTest
-  void test_string_multi_unterminated() {
-    // TODO(paulberry,ahe): bad error recovery.
-    super.test_string_multi_unterminated();
-  }
-
-  @override
-  @failingTest
   void test_string_multi_unterminated_interpolation_block() {
     // TODO(paulberry,ahe): bad error recovery.
     super.test_string_multi_unterminated_interpolation_block();
@@ -262,41 +255,6 @@ main() {}
 
   @override
   @failingTest
-  void test_string_raw_multi_unterminated() {
-    // TODO(paulberry,ahe): bad error recovery.
-    super.test_string_raw_multi_unterminated();
-  }
-
-  @override
-  @failingTest
-  void test_string_raw_simple_unterminated_eof() {
-    // TODO(paulberry,ahe): bad error recovery.
-    super.test_string_raw_simple_unterminated_eof();
-  }
-
-  @override
-  @failingTest
-  void test_string_raw_simple_unterminated_eol() {
-    // TODO(paulberry,ahe): bad error recovery.
-    super.test_string_raw_simple_unterminated_eol();
-  }
-
-  @override
-  @failingTest
-  void test_string_simple_unterminated_eof() {
-    // TODO(paulberry,ahe): bad error recovery.
-    super.test_string_simple_unterminated_eof();
-  }
-
-  @override
-  @failingTest
-  void test_string_simple_unterminated_eol() {
-    // TODO(paulberry,ahe): bad error recovery.
-    super.test_string_simple_unterminated_eol();
-  }
-
-  @override
-  @failingTest
   void test_string_simple_unterminated_interpolation_block() {
     // TODO(paulberry,ahe): bad error recovery.
     super.test_string_simple_unterminated_interpolation_block();
@@ -339,6 +297,120 @@ main() {}
 abstract class ScannerTest_Fasta_Base {
   Token scan(String source);
 
+  expectToken(Token token, TokenType type, int offset, int length,
+      {bool isSynthetic: false, String lexeme}) {
+    String description = '${token.type} $token';
+    expect(token.type, type, reason: description);
+    expect(token.offset, offset, reason: description);
+    expect(token.length, length, reason: description);
+    expect(token.isSynthetic, isSynthetic, reason: description);
+    if (lexeme != null) {
+      expect(token.lexeme, lexeme, reason: description);
+    }
+  }
+
+  void test_incomplete_string_interpolation() {
+    Token token = scan(r'"foo ${bar');
+    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');
+
+    // Expect interpolation to be terminated before string is closed
+    token = token.next;
+    expectToken(token, TokenType.CLOSE_CURLY_BRACKET, 10, 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, 10, 0, isSynthetic: true, lexeme: '"');
+
+    token = token.next;
+    expect((token as fasta.ErrorToken).errorCode, same(codeUnterminatedString));
+  }
+
+  void test_string_multi_unterminated() {
+    Token token = scan("'''string");
+    expectToken(token, TokenType.STRING, 0, 9, lexeme: "'''string");
+
+    token = token.next;
+    expectToken(token, TokenType.STRING, 9, 0,
+        isSynthetic: true, lexeme: "'''");
+
+    token = token.next;
+    expect((token as fasta.ErrorToken).errorCode, same(codeUnterminatedString));
+    expect((token as fasta.ErrorToken).start, "'''");
+  }
+
+  void test_string_raw_multi_unterminated() {
+    Token token = scan("r'''string");
+    expectToken(token, TokenType.STRING, 0, 10, lexeme: "r'''string");
+
+    token = token.next;
+    expectToken(token, TokenType.STRING, 10, 0,
+        isSynthetic: true, lexeme: "'''");
+
+    token = token.next;
+    expect((token as fasta.ErrorToken).errorCode, same(codeUnterminatedString));
+    expect((token as fasta.ErrorToken).start, "r'''");
+  }
+
+  void test_string_raw_simple_unterminated_eof() {
+    Token token = scan("r'string");
+    expectToken(token, TokenType.STRING, 0, 8, lexeme: "r'string");
+
+    token = token.next;
+    expectToken(token, TokenType.STRING, 8, 0, isSynthetic: true, lexeme: "'");
+
+    token = token.next;
+    expect((token as fasta.ErrorToken).errorCode, same(codeUnterminatedString));
+    expect((token as fasta.ErrorToken).start, "r'");
+  }
+
+  void test_string_raw_simple_unterminated_eol() {
+    Token token = scan("r'string\n");
+    expectToken(token, TokenType.STRING, 0, 8, lexeme: "r'string");
+
+    token = token.next;
+    expectToken(token, TokenType.STRING, 8, 0, isSynthetic: true, lexeme: "'");
+
+    token = token.next;
+    expect((token as fasta.ErrorToken).errorCode, same(codeUnterminatedString));
+    expect((token as fasta.ErrorToken).start, "r'");
+  }
+
+  void test_string_simple_unterminated_eof() {
+    Token token = scan("'string");
+    expectToken(token, TokenType.STRING, 0, 7, lexeme: "'string");
+
+    token = token.next;
+    expectToken(token, TokenType.STRING, 7, 0, isSynthetic: true, lexeme: "'");
+
+    token = token.next;
+    expect((token as fasta.ErrorToken).errorCode, same(codeUnterminatedString));
+    expect((token as fasta.ErrorToken).start, "'");
+  }
+
+  void test_string_simple_unterminated_eol() {
+    Token token = scan("'string\n");
+    expectToken(token, TokenType.STRING, 0, 7, lexeme: "'string");
+
+    token = token.next;
+    expectToken(token, TokenType.STRING, 7, 0, isSynthetic: true, lexeme: "'");
+
+    token = token.next;
+    expect((token as fasta.ErrorToken).errorCode, same(codeUnterminatedString));
+    expect((token as fasta.ErrorToken).start, "'");
+  }
+
   void test_match_angle_brackets() {
     var x = scan('x<y>');
     var lessThan = x.next as BeginToken;
@@ -500,32 +572,6 @@ 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