Use messages for (some) public API errors

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;
 
+import 'fasta_codes.dart' show Message, LocatedMessage, Code;
+
 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;
@@ skipping 46 matching lines @@
 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.
   return red(message);
 }
 
-class deprecated_InputError {
+class deprecated_InputError implements LocatedMessage {

[ahe, 2017/07/12 13:14:43]

I would like to maintain the invariant that instances of Message or
LocatedMessage are derived from a message in messages.yaml. So it would be great
if deprecated_InputError doesn't implement LocatedMessage.

This is how I handle the similar situation in verifier.dart:

  problem(TreeNode node, String details, {TreeNode context}) {
    context ??= this.context;
    VerificationError error = new VerificationError(context, node, details);
    CompilerContext.current.report(
        templateUnspecified
            .withArguments("$error")
            .withLocation(Uri.parse(fileUri), node?.fileOffset ?? -1),
        Severity.error);
    errors.add(error);
  }

CompilerContext.current.report is something that I've added based on what we
discussed in CL 2979713002, and should make it easier to hook up the reporting
you're adding with this CL.

[Siggi Cherem (dart-lang), 2017/07/12 21:54:59]

Done (removed the implements here)

   final Uri uri;
 
   final int charOffset;
 
   final Object error;
 
+  String get message => safeToString(error);
+
+  Message get messageObject => null;
+
+  Code get code => null;
+
+  Map<String, dynamic> get arguments => {};
+
+  String get tip => null;
+
   deprecated_InputError(this.uri, int charOffset, this.error)
       : this.charOffset = charOffset ?? -1;
 
   toString() => "deprecated_InputError: $error";
 
   String deprecated_format() =>
       deprecated_formatUnexpected(uri, charOffset, safeToString(error));
 }
 
 class Crash {
@@ skipping 77 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.";
   }
 }