Emit a compile-time error when returning a value from a constructor.

sdk/lib/_internal/compiler/implementation/warnings.dart

 // Copyright (c) 2011, 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.
 
 part of dart2js;
 
 const DONT_KNOW_HOW_TO_FIX = "";
 
 /**
  * The messages in this file should meet the following guide lines:
@@ skipping 482 matching lines @@
 
   static const MessageKind OPERATOR_OPTIONAL_PARAMETERS = const MessageKind(
       'Error: Operator "#{operatorName}" cannot have optional parameters.');
 
   static const MessageKind OPERATOR_NAMED_PARAMETERS = const MessageKind(
       'Error: Operator "#{operatorName}" cannot have named parameters.');
 
   static const MessageKind CONSTRUCTOR_WITH_RETURN_TYPE = const MessageKind(
       'Error: Cannot have return type for constructor.');
 
+  static const MessageKind CANNOT_RETURN_FROM_CONSTRUCTOR = const MessageKind(
+      "Error: Cannot return a value from a constructor.",

[ahe, 2013/09/05 08:35:20]

Prefer "can't" over "cannot" (the guidelines were updated based on feedback from
usability experts and tech writers).

+      howToFix: "Remove the return statement or use a factory constructor.",
+      examples: const ["""
+class C {
+  C() {
+    return 1;
+  }
+}
+
+main() => new C();"""]);
+
   static const MessageKind ILLEGAL_FINAL_METHOD_MODIFIER = const MessageKind(
       'Error: Cannot have final modifier on method.');
 
   static const MessageKind ILLEGAL_CONSTRUCTOR_MODIFIERS = const MessageKind(
       'Error: Illegal constructor modifiers: "#{modifiers}".');
 
   static const MessageKind ILLEGAL_MIXIN_APPLICATION_MODIFIERS =
       const MessageKind(
           'Error: Illegal mixin application modifiers: "#{modifiers}".');
 
@@ skipping 512 matching lines @@
 
 class CompileTimeConstantError extends Diagnostic {
   CompileTimeConstantError(MessageKind kind, Map arguments, bool terse)
     : super(kind, arguments, terse);
 }
 
 class CompilationError extends Diagnostic {
   CompilationError(MessageKind kind, Map arguments, bool terse)
     : super(kind, arguments, terse);
 }