Fix co19 crashes

dart/frog/leg/scanner/parser.dart

 // Copyright (c) 2012, 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.
 
 /**
  * An event generating parser of Dart programs. This parser expects
  * all tokens in a linked list.
  */
 class Parser {
   final Listener listener;
@@ skipping 417 matching lines @@
     mayParseFunctionExpressions = old;
     listener.endInitializers(count, begin, token);
     return token;
   }
 
   Token parseScriptTags(Token token) {
     Token begin = token;
     listener.beginScriptTag(token);
     token = parseIdentifier(token.next);
     token = expect('(', token);
-    token = parseLiteralString(token);
+    token = parseLiteralStringOrRecoverExpression(token);
     bool hasPrefix = false;
     if (optional(',', token)) {
       hasPrefix = true;
       token = parseIdentifier(token.next);
       token = expect(':', token);
-      token = parseLiteralString(token);
+      token = parseLiteralStringOrRecoverExpression(token);
     }
     token = expect(')', token);
     listener.endScriptTag(hasPrefix, begin, token);
     return expectSemicolon(token);
   }
 
+  Token parseLiteralStringOrRecoverExpression(Token token) {
+    if (token.kind === STRING_TOKEN) {
+      return parseLiteralString(token);
+    } else {
+      listener.recoverableError("unexpected", token: token);
+      return parseExpression(token);
+    }
+  }
+
   Token expectSemicolon(Token token) {
     return expect(';', token);
   }
 
   Token parseModifier(Token token) {
     assert(('final' === token.stringValue) ||
            ('var' === token.stringValue) ||
            ('const' === token.stringValue) ||
            ('abstract' === token.stringValue) ||
            ('static' === token.stringValue));
@@ skipping 1118 matching lines @@
     }
     listener.handleContinueStatement(hasTarget, continueKeyword, token);
     return expectSemicolon(token);
   }
 
   Token parseEmptyStatement(Token token) {
     listener.handleEmptyStatement(token);
     return expectSemicolon(token);
   }
 }