Share the first error messages.

pkg/dart_messages/lib/shared_messages.dart

Index: pkg/dart_messages/lib/shared_messages.dart
diff --git a/pkg/dart_messages/lib/shared_messages.dart b/pkg/dart_messages/lib/shared_messages.dart
index 896f52ad546ca0ba5ac6e68adc638515fe891263..5967b13ab6bd09bc4e269e3a3e422e2d9cf29e8a 100644
--- a/pkg/dart_messages/lib/shared_messages.dart
+++ b/pkg/dart_messages/lib/shared_messages.dart
@@ -70,17 +70,25 @@ class Category {
 
   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
@@ -90,23 +98,37 @@ class Message {
   // 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);
@@ -119,17 +141,73 @@ final Map<String, Message> MESSAGES = {
       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();"""
+      ]),
 };