Reapply: "Emit compile-time error on duplicate parameter names in typedefs."

sdk/lib/_internal/compiler/implementation/dart_backend/placeholder_collector.dart

Index: sdk/lib/_internal/compiler/implementation/dart_backend/placeholder_collector.dart
diff --git a/sdk/lib/_internal/compiler/implementation/dart_backend/placeholder_collector.dart b/sdk/lib/_internal/compiler/implementation/dart_backend/placeholder_collector.dart
index a4e367fa563b7728a987de57d5cf4a04ea97b828..6f07e12c58016fd610c71e9a1185911a389e557f 100644
--- a/sdk/lib/_internal/compiler/implementation/dart_backend/placeholder_collector.dart
+++ b/sdk/lib/_internal/compiler/implementation/dart_backend/placeholder_collector.dart
@@ -244,6 +244,13 @@ class PlaceholderCollector extends Visitor {
     });
   }
 
+  // TODO(karlklose): should we create placeholders for these?
+  bool isTypedefParameter(Element element) {
+    return element != null &&
+        element.enclosingElement != null &&
+        element.enclosingElement.isTypedef();
+  }
+
   void tryMakeLocalPlaceholder(Element element, Identifier node) {
     bool isNamedOptionalParameter() {
       FunctionElement function = element.enclosingElement;
@@ -258,9 +265,10 @@ class PlaceholderCollector extends Visitor {
     // TODO(smok): Maybe we should rename privates as well, their privacy
     // should not matter if they are local vars.
     if (node.source.isPrivate()) return;
-    if (element.isParameter() && isNamedOptionalParameter()) {
+    if (element.isParameter() && !isTypedefParameter(element) &&
+        isNamedOptionalParameter()) {
       currentFunctionScope.registerParameter(node);
-    } else if (Elements.isLocal(element)) {
+    } else if (Elements.isLocal(element) && !isTypedefParameter(element)) {

[Johnni Winther, 2013/09/23 08:06:18]

How can this happen?

[karlklose, 2013/09/23 08:09:52]

Typedef parameters are parameters that are not instance members, and not
top-level or static.

       makeLocalPlaceholder(node);
     }
   }