The very first bits of resynthesizing elements from kernels.

pkg/front_end/lib/src/fasta/deprecated_problems.dart

 // Copyright (c) 2016, 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.errors;
 
 import 'dart:async' show Future;
 
 import 'dart:convert' show JSON;
 
 import 'dart:io'
     show ContentType, HttpClient, HttpClientRequest, SocketException, stderr;
 
 import 'colors.dart' show red;
 
 import 'messages.dart' show errorsAreFatal, deprecated_format, isVerbose;
 
 const String defaultServerAddress = "http://127.0.0.1:59410/";
 
 /// Tracks if there has been a crash reported through [reportCrash]. Should be
 /// reset between each compilation by calling [resetCrashReporting].
 bool hasCrashed = false;
 
 /// Tracks the first source URI that has been read and is used as a fall-back
 /// for [reportCrash]. Should be reset between each compilation by calling
 /// [resetCrashReporting].
 Uri firstSourceUri;
 
+/// This flag is a temporary solution for preventing printing a lot
+/// of information on the console. Analyzer starts using Fasta to generate
+/// kernels to resynthesize its element models from it. We don't want to
+/// see all these errors and warnings on the console, while running test or
+/// in production. TODO(scheglov): remove this flag eventually.
+bool temporaryUntilPrintsRemovedEnablePrinting = true;
+
 /// Used to report an error in input.
 ///
 /// Avoid using this for reporting compile-time errors, instead use
 /// `LibraryBuilder.addCompileTimeError` for those.
 ///
 /// An input error is any error that isn't an internal error. We use the term
 /// "input error" in favor of "user error". This way, if an input error isn't
 /// handled correctly, the user will never see a stack trace that says "user
 /// error".
 dynamic deprecated_inputError(Uri uri, int charOffset, Object error) {
   if (errorsAreFatal && isVerbose) {
     print(StackTrace.current);
   }
   throw new deprecated_InputError(uri, charOffset, error);
 }
 
 String deprecated_printUnexpected(Uri uri, int charOffset, String message) {
   String formattedMessage =
       deprecated_formatUnexpected(uri, charOffset, message);
   if (errorsAreFatal) {
     print(formattedMessage);
     if (isVerbose) print(StackTrace.current);
     throw new deprecated_InputError(uri, charOffset, message);
   }
-  print(formattedMessage);
+  if (temporaryUntilPrintsRemovedEnablePrinting) {
+    print(formattedMessage);
+  }
   return formattedMessage;
 }
 
 String deprecated_formatUnexpected(Uri uri, int charOffset, String message) {
   return deprecated_format(uri, charOffset, colorError("Error: $message"));
 }
 
 String colorError(String message) {
   // TODO(ahe): Colors need to be optional. Doesn't work well in Emacs or on
   // Windows.
@@ skipping 97 matching lines @@
   return new Future.error(error, trace);
 }
 
 String safeToString(Object object) {
   try {
     return "$object";
   } catch (e) {
     return "Error when converting ${object.runtimeType} to string.";
   }
 }