Remove flag for enabling null-aware operators. They are now on by default.

pkg/compiler/lib/src/scanner/scanner.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.
 
 part of scanner;
 
 abstract class Scanner {
   Token tokenize();
 
   factory Scanner(SourceFile file,
-      {bool includeComments: false, bool enableNullAwareOperators: false}) {
+      {bool includeComments: false}) {
     if (file is Utf8BytesSourceFile) {
-      return new Utf8BytesScanner(file, includeComments: includeComments,
-          enableNullAwareOperators: enableNullAwareOperators);
+      return new Utf8BytesScanner(file, includeComments: includeComments);
     } else {
-      return new StringScanner(file, includeComments: includeComments,
-          enableNullAwareOperators: enableNullAwareOperators);
+      return new StringScanner(file, includeComments: includeComments);
     }
   }
 }
 
 abstract class AbstractScanner implements Scanner {
   // TODO(ahe): Move this class to implementation.
 
   final bool includeComments;
-  final bool enableNullAwareOperators;
 
   /**
    * The string offset for the next token that will be created.
    *
    * Note that in the [Utf8BytesScanner], [stringOffset] and [scanOffset] values
    * are different. One string character can be encoded using multiple UTF-8
    * bytes.
    */
   int tokenStart = -1;
 
@@ skipping 14 matching lines @@
   /**
    * The source file that is being scanned. This field can be [:null:].
    * If the source file is available, the scanner assigns its [:lineStarts:] and
    * [:length:] fields at the end of [tokenize].
    */
   final SourceFile file;
 
   final List<int> lineStarts = <int>[0];
 
   AbstractScanner(
-      this.file, this.includeComments, this.enableNullAwareOperators) {
+      this.file, this.includeComments) {
     this.tail = this.tokens;
   }
 
   /**
    * Advances and returns the next character.
    *
    * If the next character is non-ASCII, then the returned value depends on the
    * scanner implementation. The [Utf8BytesScanner] returns a UTF-8 byte, while
    * the [StringScanner] returns a UTF-16 code unit.
    *
@@ skipping 379 matching lines @@
 
   int tokenizeCaret(int next) {
     // ^ ^=
     return select($EQ, CARET_EQ_INFO, CARET_INFO);
   }
 
   int tokenizeQuestion(int next) {
     // ? ?. ?? ??=
     next = advance();
     if (identical(next, $QUESTION)) {
-      if (enableNullAwareOperators) {
-        return select($EQ, QUESTION_QUESTION_EQ_INFO, QUESTION_QUESTION_INFO);
-      } else {
-        next = advance();
-        PrecedenceInfo info;
-        if (identical(next, $EQ)) {
-          info = QUESTION_QUESTION_EQ_INFO;
-          next = advance();
-        } else {
-          info = QUESTION_QUESTION_INFO;
-        }
-        appendErrorToken(new UnsupportedNullAwareToken(info.value, tokenStart));
-        return next;
-      }
+      return select($EQ, QUESTION_QUESTION_EQ_INFO, QUESTION_QUESTION_INFO);
     } else if (identical(next, $PERIOD)) {
-      if (enableNullAwareOperators) {
-        appendPrecedenceToken(QUESTION_PERIOD_INFO);
-      } else {
-        appendErrorToken(new UnsupportedNullAwareToken(
-            QUESTION_PERIOD_INFO.value, tokenStart));
-      }
+      appendPrecedenceToken(QUESTION_PERIOD_INFO);
       return advance();
     } else {
       appendPrecedenceToken(QUESTION_INFO);
       return next;
     }
   }
 
   int tokenizeBar(int next) {
     // | || |=
     next = advance();
@@ skipping 691 matching lines @@
 
 PrecedenceInfo closeBraceInfoFor(BeginGroupToken begin) {
   return const {
     '(': CLOSE_PAREN_INFO,
     '[': CLOSE_SQUARE_BRACKET_INFO,
     '{': CLOSE_CURLY_BRACKET_INFO,
     '<': GT_INFO,
     r'${': CLOSE_CURLY_BRACKET_INFO,
   }[begin.value];
 }