Second round of cleanups for new optional parameter semantics.

lib/compiler/implementation/dart_backend/placeholder_collector.dart

 // Copyright (c) 2012, 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.
 
 class LocalPlaceholder {
   final String identifier;
   final Set<Node> nodes;
   LocalPlaceholder(this.identifier) : nodes = new Set<Node>();
   int hashCode() => identifier.hashCode();
   String toString() =>
@@ skipping 115 matching lines @@
     collector.makeElementPlaceholder(node.selector, element);
     // Another ugly case: <lib prefix>.<top level> is represented as
     // receiver: lib prefix, selector: top level.
     if (element.isTopLevel() && node.receiver != null) {
       assert(elements[node.receiver].isPrefix());
       // Hack: putting null into map overrides receiver of original node.
       collector.makeNullPlaceholder(node.receiver);
     }
   }
 
-  internalError(String reason, [Node node]) {
+  internalError(String reason, {Node node}) {
     collector.internalError(reason, node);
   }
 }
 
 class PlaceholderCollector extends Visitor {
   final Compiler compiler;
   final Set<String> fixedMemberNames; // member names which cannot be renamed.
   final Map<Element, ElementAst> elementAsts;
   final Set<Node> nullNodes;  // Nodes that should not be in output.
   final Set<Identifier> unresolvedNodes;
@@ skipping 489 matching lines @@
 
   visitBlock(Block node) {
     for (Node statement in node.statements.nodes) {
       if (statement is VariableDefinitions) {
         makeVarDeclarationTypePlaceholder(statement);
       }
     }
     node.visitChildren(this);
   }
 }