Share the first error messages.

pkg/dart_messages/lib/shared_messages.dart

 // Copyright (c) 2015, 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.
 
 // An update to this file must be followed by regenerating the corresponding
 // json, dart2js and analyzer file. Use `publish.dart` in the bin directory.
 //
 // Every message in this file must have an id. Use `message_id.dart` in the
 // bin directory to generate a fresh one.
 
@@ skipping 52 matching lines @@
 /// Encodes the category of the message.
 ///
 /// This is currently only used in the analyzer.
 // TODO(floitsch): encode severity and type in the category, so we can generate
 // the corresponding ErrorCode subclasses.
 class Category {
   static final analysisOptionsError = new Category("AnalysisOptionsError");
 
   static final analysisOptionsWarning = new Category("AnalysisOptionsWarning");
 
-  static final checkedModeCompileTimeError = new Category(
-      "CheckedModeCompileTimeError");
+  static final checkedModeCompileTimeError =
+      new Category("CheckedModeCompileTimeError");
+
+  static final parserError = new Category("ParserError");
 
   final String name;
 
   Category(this.name);
 }
 
+enum Platform {
+  dart2js, analyzer,
+}
+const dart2js = Platform.dart2js;
+const analyzer = Platform.analyzer;
 
 class Message {
   final String id;
+  final int subId;
   final Category category;
   final String template;
   // The analyzer fills holes positionally (and not named). The following field
   // overrides the order of the holes.
   // For example the template "The argument #field in #cls is bad", could have
   // the order `["cls", "field"]', which means that the analyzer would first
   // provide the class `cls` and then only `field`.
   // This list is generally `null`, but when it is provided it must contain all
   // holes.
-  final List templateHoleOrder;
+  final List<String> templateHoleOrder;
   final String howToFix;
   final List<String> options;
   final List examples;
+  final List<Platform> usedBy;
 
-  Message({this.id, this.category, this.template, this.templateHoleOrder,
-      this.howToFix, this.options, this.examples});
+  Message(
+      {this.id,
+      this.subId: 0,
+      this.category,
+      this.template,
+      this.templateHoleOrder,
+      this.howToFix,
+      this.options,
+      this.usedBy: const [],
+      this.examples});
 }
 
 String get messagesAsJson {
   var jsonified = {};
   MESSAGES.forEach((String name, Message message) {
-    jsonified[name] =  {
+    jsonified[name] = {
       'id': message.id,
+      'subId': message.subId,
       'category': message.category.name,
       'template': message.template,
-      'howToFix': message.howToFix
+      'templateHoleOrder': message.templateHoleOrder,
+      'howToFix': message.howToFix,
+      'options': message.options,
+      'usedBy': message.usedBy.map((platform) => platform.toString()).toList(),
+      'examples': message.examples,
     };
   });
   return JSON.encode(jsonified);
 }
 
 final Map<String, Message> MESSAGES = {
   'exampleMessage': new Message(
       id: 'use an Id generated by bin/message_id.dart',
       category: Category.analysisOptionsError,
       template: "#use #named #arguments",
       templateHoleOrder: ["arguments", "named", "use"],
       howToFix: "an explanation on how to fix things",
-      examples: [r'''
+      examples: [
+        r'''
       Some multiline example;
       That generates the bug.''',
-      {
-      'fileA.dart': '''
+        {
+          'fileA.dart': '''
         or a map from file to content.
         again multiline''',
-      'fileB.dart': '''
+          'fileB.dart': '''
         with possibly multiple files.
         muliline too'''
-      }
-    ]
-  ),
+        }
+      ]),
+
+  // Const constructors (factory or not) may not have a body.
+  'CONST_CONSTRUCTOR_HAS_BODY': new Message(
+      id: 'LGJGHW',
+      category: Category.parserError,

[Brian Wilkerson, 2016/02/03 00:27:12]

Missing subId?

[floitsch, 2016/02/03 17:50:25]

Missing subid implies 0, but I added it.

[Brian Wilkerson, 2016/02/03 20:37:22]

Good to know.

+      template: "Const constructor or factory can't have a body.",
+      howToFix: "Remove the 'const' keyword or the body.",
+      usedBy: [dart2js],
+      examples: const [
+        r"""
+         class C {
+           const C() {}
+         }
+
+         main() => new C();""",
+        r"""
+         class C {
+           const factory C() {}
+         }
+
+         main() => new C();"""
+      ]),
+  // Const constructors may not have a body.
+  'CONST_CONSTRUCTOR_WITH_BODY': new Message(
+      id: 'LGJGHW',
+      subId: 1,
+      category: Category.parserError,
+      template: "Const constructor or factory can't have a body.",

[Brian Wilkerson, 2016/02/03 00:27:12]

The "or factory" is confusing. If the constructor is a factory constructor the
CONST_FACTORY message will be used. Hence this message should not mention
factories.

Which means that we can revert this to the current message. Note that every time
we change a message we risk breaking one of the post-processing tools that are
matching the message. (I wish there weren't any such tools, but until we get
stable id's and convert the tools to use them we're kind of stuck.)

[floitsch, 2016/02/03 17:50:25]

My mistake. Removed the factory part.
I don't want to use the original message, since it starts with a lower case
character.
If you feel strongly, I will change, though.

[Brian Wilkerson, 2016/02/03 20:37:22]

Like I said, every time we change a message we risk breaking someone. But if you
do change it I would expect "Const constructors cannot have a body." (or
"can't", if we're being informal).

[floitsch, 2016/02/03 21:15:39]

The latest version is "Const constructor cannot have a body". (Is it, that you
want to make it plural?)

I agree with you that changing the error-messages is dangerous. However, I don't
expect anyone to grep for this particular message. That just should never happen
in code.

[Brian Wilkerson, 2016/02/03 21:30:59]

Sounds good.
Nope.
True. Probably more of an issue for warnings and hints.

+      howToFix: "Remove the 'const' keyword or the body.",
+      usedBy: [analyzer],
+      examples: const [
+        r"""
+         class C {
+           const C() {}
+         }
+
+         main() => new C();"""
+      ]),
+  // Const constructor factories may only redirect (and must not have a body).
+  'CONST_FACTORY': new Message(
+      id: 'LGJGHW',
+      subId: 2,
+      category: Category.parserError,
+      template:
+          "Only redirecting factory constructors can be declared to be 'const'",
+      howToFix: "Remove the 'const' keyword or replace the body with '=' "
+          "followed by a valid target",
+      usedBy: [analyzer],
+      examples: const [
+        r"""
+         class C {
+           const factory C() {}
+         }
+
+         main() => new C();"""
+      ]),
 };