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 363 matching lines @@
       warning: const MessageKind(
           'Warning: Cannot refer to type variable "#{typeVariableName}" '
           'within a static member.'));
 
   static const MessageKind TYPE_VARIABLE_IN_CONSTANT = const MessageKind(
       'Error: Cannot refer to type variable in constant.');
 
   static const MessageKind INVALID_TYPE_VARIABLE_BOUND = const MessageKind(
       "Warning: '#{typeArgument}' is not a subtype of bound '#{bound}' for "
       "type variable '#{typeVariable}' of type '#{thisType}'.",
       howToFix: "Try to change or remove the type argument.",

[Kathy Walrath, 2013/09/13 17:59:08]

Try to change or remove
->
Try changing or removing

("Try to blank" is fine, grammatically, but it's inconsistent with the "Try
blanking" wording elsewhere in these messages.)

       examples: const ["""
 class C<T extends num> {}
 
 // 'String' is not a valid instantiation of T with bound num.'.
 main() => new C<String>();
 """]);
 
   static const MessageKind INVALID_USE_OF_SUPER = const MessageKind(
       'Error: "super" not allowed here.');
 
@@ skipping 27 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.",

[Kathy Walrath, 2013/09/13 17:59:08]

default a value -> a default value

[karlklose, 2013/09/16 07:58:59]

Done.

+      howToFix:
+        "Try removing the default value or make the parameter optional.",

[Kathy Walrath, 2013/09/13 17:59:08]

This should be:

Try removing the default value or making the parameter optional.

[karlklose, 2013/09/16 07:58:59]

Done.

+      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 use ':' to specify a default value.",

[Kathy Walrath, 2013/09/13 17:59:08]

Shouldn't this mention/describe the error/problem? Maybe:

Error: Named parameters can't use '=' to specify a default value.

[karlklose, 2013/09/16 07:58:59]

Done.

+      howToFix: "Try replacing '=' with ':'.",
+      examples: const ["""
+main() {
+  foo({a = 1}) => print(a);
+  foo(a: 2);
+}"""]);
+
+  static const MessageKind POSITIONAL_PARAMETER_WITH_EQUALS = const MessageKind(
+      "Error: Positional optional parameters use '=' to specify a default "

[Kathy Walrath, 2013/09/13 17:59:08]

Again, this doesn't describe the error. Maybe: 

Error: Positional optional parameters can't use ':' to specify a default value.

[karlklose, 2013/09/16 07:58:59]

Done.

+      "value.",
+      howToFix: "Try replacing ':' with '='.",
+      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.",
+      howToFix:
+        "Try removing the default value or making the parameter optional.",
       examples: const ["""
 typedef void F([int arg = 0]);
 
 main() {
   F f;
 }""", """
 typedef void F({int arg: 0});
 
 main() {
   F f;
@@ skipping 666 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);
 }