Issue 4289. Separate optional positional and named parameters

compiler/java/com/google/dart/compiler/parser/DartParser.java

Index: compiler/java/com/google/dart/compiler/parser/DartParser.java
diff --git a/compiler/java/com/google/dart/compiler/parser/DartParser.java b/compiler/java/com/google/dart/compiler/parser/DartParser.java
index 4b51d39f83f3ade150d3b54369d9ab355149b112..9b206f9c869092ee62ae852769976e420628ed96 100644
--- a/compiler/java/com/google/dart/compiler/parser/DartParser.java
+++ b/compiler/java/com/google/dart/compiler/parser/DartParser.java
@@ -1709,6 +1709,9 @@ public class DartParser extends CompletionHooksParserBase {
       }
       // In methods with required arity each parameter is required.
       for (DartParameter parameter : parameters) {
+        if (parameter.getModifiers().isOptional()) {
+          reportError(parameter, ParserErrorCode.OPTIONAL_POSITIONAL_PARAMETER_NOT_ALLOWED);
+        }
         if (parameter.getModifiers().isNamed()) {
           reportError(parameter, ParserErrorCode.NAMED_PARAMETER_NOT_ALLOWED);
         }
@@ -2139,8 +2142,6 @@ public class DartParser extends CompletionHooksParserBase {
 
     if (isOptional) {
       modifiers = modifiers.makeOptional();
-      // TODO(brianwilkerson) Remove the line below when we no longer need to support the old syntax.
-      modifiers = modifiers.makeNamed();
     }
     if (isNamed) {
       modifiers = modifiers.makeNamed();