Complain about incorrect use of null-aware operations.

pkg/front_end/lib/src/fasta/parser/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.
 
 library fasta.parser.parser;
 
 import '../fasta_codes.dart'
     show
         FastaCode,
         FastaMessage,
@@ skipping 33 matching lines @@
         codeInvalidVoid,
         codeNoFormals,
         codeNonAsciiIdentifier,
         codeNonAsciiWhitespace,
         codeOnlyTry,
         codePositionalParameterWithEquals,
         codePrivateNamedParameter,
         codeRequiredParameterWithDefault,
         codeSetterNotSync,
         codeStackOverflow,
+        codeSuperNullAware,
         codeTypeAfterVar,
         codeTypeRequired,
         codeUnexpectedToken,
         codeUnmatchedToken,
         codeUnspecified,
         codeUnsupportedPrefixPlus,
         codeUnterminatedString,
         codeYieldAsIdentifier,
         codeYieldNotGenerator;
 
@@ skipping 2986 matching lines @@
 
   Token parseSuperExpression(Token token, IdentifierContext context) {
     Token beginToken = token;
     listener.handleSuperExpression(token, context);
     token = token.next;
     if (optional('(', token)) {
       // Super constructor.
       listener.handleNoTypeArguments(token);
       token = parseArguments(token);
       listener.endSend(beginToken, token);
+    } else if (optional("?.", token)) {
+      reportRecoverableErrorCode(token, codeSuperNullAware);
     }
     return token;
   }
 
   /// '[' (expressionList ','?)? ']'.
   ///
   /// Provide [constKeyword] if preceded by 'const', null if not.
   /// This is a suffix parser because it is assumed that type arguments have
   /// been parsed, or `listener.handleNoTypeArguments(..)` has been executed.
   Token parseLiteralListSuffix(Token token, Token constKeyword) {
@@ skipping 930 matching lines @@
     return reportUnrecoverableError(
         token, () => code.format(uri, token.charOffset, string));
   }
 }
 
 typedef FastaMessage NoArgument(Uri uri, int charOffset);
 
 typedef FastaMessage TokenArgument(Uri uri, int charOffset, Token token);
 
 typedef FastaMessage StringArgument(Uri uri, int charOffset, String string);