Issue 4289. Separate optional positional and named parameters

compiler/java/com/google/dart/compiler/ast/DartToSourceVisitor.java

Index: compiler/java/com/google/dart/compiler/ast/DartToSourceVisitor.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartToSourceVisitor.java b/compiler/java/com/google/dart/compiler/ast/DartToSourceVisitor.java
index 2d4d80a536a7ff813d670e82ec7b209fbd0475a4..57fd177b9d624022ecbb1a49456769ba759d4853 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartToSourceVisitor.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartToSourceVisitor.java
@@ -255,7 +255,12 @@ public class DartToSourceVisitor extends ASTVisitor<Void> {
       p(")");
     }
     if (x.getDefaultExpr() != null) {
-      p(" = ");
+      if (x.getModifiers().isOptional()) {
+        p(" = ");
+      }
+      if (x.getModifiers().isNamed()) {
+        p(" : ");
+      }
       accept(x.getDefaultExpr());
     }
     return null;
@@ -348,21 +353,28 @@ public class DartToSourceVisitor extends ASTVisitor<Void> {
   }
 
   private void pFormalParameters(List<DartParameter> params) {
-    boolean first = true, hasNamed = false;
+    boolean first = true, hasPositional = false, hasNamed = false;
     for (DartParameter param : params) {
       if (!first) {
         p(", ");
       }
+      if (!hasPositional && param.getModifiers().isOptional()) {
+        hasPositional = true;
+        p("[");
+      }
       if (!hasNamed && param.getModifiers().isNamed()) {
         hasNamed = true;
-        p("[");
+        p("{");
       }
       accept(param);
       first = false;
     }
-    if (hasNamed) {
+    if (hasPositional) {
       p("]");
     }
+    if (hasNamed) {
+      p("}");
+    }
   }
   
   @Override