Emit compile-time error for incorrectly used optional parameters.

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 400 matching lines @@
 
   static const DualKind NO_SUCH_LIBRARY_MEMBER = const DualKind(
       error: const MessageKind(
           'Error: "#{libraryName}" has no member named "#{memberName}".'),
       warning: const MessageKind(
           'Warning: "#{libraryName}" has no member named "#{memberName}".'));
 
   static const MessageKind CANNOT_INSTANTIATE_TYPEDEF = const MessageKind(
       'Error: Cannot instantiate typedef "#{typedefName}".');
 
+  static const MessageKind REQUIRED_PARAMETER_WITH_DEFAULT = const MessageKind(
+      "Error: Non-optional parameters can't have default a value.",
+      howToFix: "Remove the default value or make the parameter optional.",

[ahe, 2013/09/13 07:17:05]

"Remove ..." sound like a command/order, could you make it sound more like a
suggestion?

+      examples: const ["""
+main() {
+  foo(a: 1) => print(a);
+  foo(2);
+}""", """
+main() {
+  foo(a = 1) => print(a);
+  foo(2);
+}"""]);
+
+  static const MessageKind NAMED_PARAMETER_WITH_EQUALS = const MessageKind(
+      "Error: Named parameters must use ':'.",

[ahe, 2013/09/13 07:17:05]

I have a suspicion that Luke would say this error message is a bit rude ;-)

How about: "A named parameter can't be followed by '=', a default value of a
named parameter is indicated with ':'."

As far as I understand Luke's advice, this follows the guide line: what is wrong
and why?

+      howToFix: "Change '=' to ':'",

[ahe, 2013/09/13 07:17:05]

Suggestion?

+      examples: const ["""
+main() {
+  foo({a = 1}) => print(a);
+  foo(a: 2);
+}"""]);
+
+  static const MessageKind POSITIONAL_PARAMETER_WITH_EQUALS = const MessageKind(
+      "Error: Positional optional parameters must use '='.",

[ahe, 2013/09/13 07:17:05]

Possibly rude, see above. 

+      howToFix: "Change ':' to '='",

[ahe, 2013/09/13 07:17:05]

Suggestion?

+      examples: const ["""
+main() {
+  foo([a: 1]) => print(a);
+  foo(2);
+}"""]);
+
   static const MessageKind TYPEDEF_FORMAL_WITH_DEFAULT = const MessageKind(
       "Error: A parameter of a typedef can't specify a default value.",
       howToFix: "Remove the default value.",
       examples: const ["""
 typedef void F([int arg = 0]);
 
 main() {
   F f;
 }""", """
 typedef void F({int arg: 0});
@@ skipping 669 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);
 }