Fix parsing of named parameters (issue 243).

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
===================================================================
--- runtime/vm/parser.cc	(revision 970)
+++ runtime/vm/parser.cc	(working copy)
@@ -930,9 +930,7 @@
     // Parse positional parameters.
     ParseFormalParameters(allow_explicit_default_values,
                           params);
-    if (CurrentToken() == Token::kLBRACK) {
-      ASSERT(!params->has_named_optional_parameters);
-      params->has_named_optional_parameters = true;
+    if (params->has_named_optional_parameters) {
       // Parse named optional parameters.
       ParseFormalParameters(allow_explicit_default_values,
                             params);
@@ -961,6 +959,7 @@
     if (!params->has_named_optional_parameters &&
         (CurrentToken() == Token::kLBRACK)) {
       // End of normal parameters, start of named parameters.
+      params->has_named_optional_parameters = true;
       return;
     }
     ParseFormalParameter(allow_explicit_default_values, params);