Implement --fatal=errors.

pkg/front_end/lib/src/fasta/errors.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' as messages;
+import 'messages.dart' show
+    areErrorsFatal,
+    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;
 
 /// Used to report an internal error.
 ///
 /// Internal errors should be avoided as best as possible, but are preferred
 /// over assertion failures. Favor error messages that starts with "Internal
 /// error: " and a short description that may help a developer debug the issue.
 /// This method should be called instead of using `throw`, as this allows us to
 /// ensure that there are no throws anywhere in the codebase.
 dynamic internalError(Object error, [Uri uri, int charOffset = -1]) {
   if (uri == null && charOffset == -1) {
     throw error;
   } else {
-    throw messages.format(
-        uri, charOffset, "Internal error: ${safeToString(error)}");
+    throw format(uri, charOffset, "Internal error: ${safeToString(error)}");
   }
 }
 
 /// 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 inputError(Uri uri, int charOffset, Object error) {
   throw new InputError(uri, charOffset, error);
 }
 
+String printUnexpected(Uri uri, int charOffset, String message) {
+  if (areErrorsFatal) {

[karlklose, 2017/02/20 12:53:10]

I would prefer to call these xxxAreFatal, because I think it looks more natural
in a conditional expression.

[ahe, 2017/02/20 13:22:34]

Done.

+    if (isVerbose) print(StackTrace.current);
+    throw new InputError(uri, charOffset, message);
+  }
+  message = formatUnexpected(uri, charOffset, message);
+  print(message);
+  return message;
+}
+
+String formatUnexpected(Uri uri, int charOffset, String message) {
+  return 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.
   return red(message);
 }
 
 class InputError {
   final Uri uri;
 
   final int charOffset;
 
   final Object error;
 
   InputError(this.uri, int charOffset, this.error)
       : this.charOffset = charOffset ?? -1;
 
   toString() => "InputError: $error";
 
-  String format() {
-    return messages.format(
-        uri, charOffset, colorError("Error: ${safeToString(error)}"));
-  }
+  String format() => formatUnexpected(uri, charOffset, safeToString(error));
 }
 
 class Crash {
   final Uri uri;
 
   final int charOffset;
 
   final Object error;
 
   final StackTrace trace;
@@ skipping 69 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.";
   }
 }