Better error handling when scanning library tags

runtime/vm/scanner.cc

 // Copyright (c) 2011, 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.
 
 #include "vm/scanner.h"
 
 #include "vm/assert.h"
 #include "vm/flags.h"
 #include "vm/object.h"
 #include "vm/thread.h"
@@ skipping 295 matching lines @@
   int ident_length = 0;
   int32_t ident_pos = lookahead_pos_;
   while (IsIdentChar(c0_) && (allow_dollar || (c0_ != '$'))) {
     ReadChar();
     ident_length++;
   }
   return String::NewSymbol(source_, ident_pos, ident_length);
 }
 
 
+void Scanner::SkipLine() {
+  while (c0_ != '\n' && c0_ != '\0') {
+    ReadChar();
+  }
+}
+
+
 void Scanner::ScanLibraryTag() {
   ReadChar();
   if (c0_ == '!') {
+    Recognize(Token::kSCRIPTTAG);
     // The script tag extends to the end of the line. Just treat this
     // similar to a line comment.
-    while (c0_ != '\n' && c0_ != '\0') {
-      ReadChar();
-    }
-    Recognize(Token::kSCRIPTTAG);
+    SkipLine();
+    return;
+  }
+  if (!IsIdentStartChar(c0_)) {
+    ErrorMsg("Unrecognized library tag");
+    SkipLine();
     return;
   }
   const String& kLibrary = String::Handle(String::NewSymbol("library"));
   const String& kImport = String::Handle(String::NewSymbol("import"));
   const String& kSource = String::Handle(String::NewSymbol("source"));
   const String& ident = String::Handle(ConsumeIdentChars(false));
   if (ident.Equals(kLibrary)) {
     current_token_.kind = Token::kLIBRARY;
     return;
   }
   if (ident.Equals(kImport)) {
     current_token_.kind = Token::kIMPORT;
     return;
   }
   if (ident.Equals(kSource)) {
     current_token_.kind = Token::kSOURCE;
     return;
   }
   ErrorMsg("Unrecognized library token");
+  SkipLine();
 }
 
 
 void Scanner::ScanLiteralString(bool is_raw) {
   ASSERT(!IsScanningString());
   ASSERT(c0_ == '"' || c0_ == '\'');
 
   // Entering string scanning mode.
   BeginStringLiteral(c0_);
   string_is_multiline_ = (LookaheadChar(1) == c0_) &&
@@ skipping 470 matching lines @@
               "%c%"PRIxPTR, kPrivateKeySeparator, key_value);
   const String& result = String::Handle(String::New(private_key));
   return result.raw();
 }
 
 
 void Scanner::InitOnce() {
 }
 
 }  // namespace dart