Initializing formals can't be optional parameters

runtime/vm/parser.cc

 // 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.
 
 #include "vm/parser.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
 #include "vm/compiler_stats.h"
@@ skipping 822 matching lines @@
     parameter.is_field_initializer = true;
   }
   // At this point, we must see an identifier for the parameter name.
   if (CurrentToken() != Token::kIDENT) {
     ErrorMsg("parameter name expected");
   }
   parameter.name = CurrentLiteral();
   parameter.name_pos = token_index_;
   ConsumeToken();
   if (parameter.is_field_initializer) {
+    if (params->has_named_optional_parameters) {

[Ivan Posva, 2011/11/22 19:58:38]

A comment explaining how this works would be nice, but I guess when you read the
whole thing you do not have it as much out of context.

+      ErrorMsg(parameter.name_pos,
+               "initializing formal parameter cannot be optional");
+    }
     params->has_field_initializer = true;
   }
 
   if (CurrentToken() == Token::kLPAREN) {
     // This parameter is probably a closure. If we saw the keyword 'var'
     // or 'final', a closure is not legal here and we ignore the
     // opening parens.
     if (!var_seen && !parameter.is_final) {
       // The parsed parameter type is actually the function result type.
       const Type& result_type = Type::Handle(parameter.type->raw());
@@ skipping 6579 matching lines @@
 }
 
 
 void Parser::SkipNestedExpr() {
   const bool saved_mode = SetAllowFunctionLiterals(true);
   SkipExpr();
   SetAllowFunctionLiterals(saved_mode);
 }
 
 }  // namespace dart