null-aware operators in the VM

runtime/vm/scanner.cc

 // 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.
 
 #include "vm/scanner.h"
 
 #include "platform/assert.h"
 #include "vm/dart.h"
 #include "vm/flags.h"
 #include "vm/object.h"
@@ skipping 768 matching lines @@
 
       case '.':  // .  ..  Number
         Recognize(Token::kPERIOD);
         if (c0_ == '.') {
           Recognize(Token::kCASCADE);
         } else if (IsDecimalDigit(c0_)) {
           ScanNumber(true);
         }
         break;
 
-      case '?':
+      case '?':  // ?  ?.  ??  ??=
         Recognize(Token::kCONDITIONAL);
+        if (c0_ == '.') {
+          Recognize(Token::kQM_PERIOD);
+        } else if (c0_ == '?') {
+          Recognize(Token::kIFNULL);
+          if (c0_ == '=') {
+            Recognize(Token::kASSIGN_COND);
+          }
+        }
         break;
 
       case ':':
         Recognize(Token::kCOLON);
         break;
 
       case ';':
         Recognize(Token::kSEMICOLON);
         break;
 
@@ skipping 164 matching lines @@
     keywords_[i].keyword_symbol = &Symbols::Keyword(token);
 
     int ch = keywords_[i].keyword_chars[0] - 'a';
     if (keywords_char_offset_[ch] == Token::kNumKeywords) {
       keywords_char_offset_[ch] = i;
     }
   }
 }
 
 }  // namespace dart