dart2js: Fix hints in code base.

pkg/compiler/lib/src/scanner/listener.dart

Index: pkg/compiler/lib/src/scanner/listener.dart
diff --git a/pkg/compiler/lib/src/scanner/listener.dart b/pkg/compiler/lib/src/scanner/listener.dart
index cd747b942560cce8e9d8fd3307a1a69227d6c4b1..b6c356a0a98b398420120888688ecb8869e2e68a 100644
--- a/pkg/compiler/lib/src/scanner/listener.dart
+++ b/pkg/compiler/lib/src/scanner/listener.dart
@@ -945,10 +945,9 @@ class ElementListener extends Listener {
   void endClassDeclaration(int interfacesCount, Token beginToken,
                            Token extendsKeyword, Token implementsKeyword,
                            Token endToken) {
-    NodeList interfaces =
-        makeNodeList(interfacesCount, implementsKeyword, null, ",");
-    Node supertype = popNode();
-    NodeList typeParameters = popNode();
+    makeNodeList(interfacesCount, implementsKeyword, null, ","); // interfaces
+    popNode(); // superType
+    popNode(); // typeParameters
     Identifier name = popNode();
     int id = idGenerator();
     PartialClassElement element = new PartialClassElement(
@@ -967,9 +966,9 @@ class ElementListener extends Listener {
   }
 
   void endFunctionTypeAlias(Token typedefKeyword, Token endToken) {
-    NodeList typeVariables = popNode(); // TOOD(karlklose): do not throw away.
+    popNode(); // TODO(karlklose): do not throw away typeVariables.
     Identifier name = popNode();
-    TypeAnnotation returnType = popNode();
+    popNode(); // returnType
     pushElement(
         new PartialTypedefElement(
             name.source, compilationUnitElement, typedefKeyword, endToken));
@@ -1010,7 +1009,7 @@ class ElementListener extends Listener {
     bool hasParseError = currentMemberHasParseError;
     memberErrors = memberErrors.tail;
     Identifier name = popNode();
-    TypeAnnotation type = popNode();
+    popNode(); // type
     Modifiers modifiers = popNode();
     PartialFunctionElement element = new PartialFunctionElement(
         name.source, beginToken, getOrSet, endToken,
@@ -1027,7 +1026,7 @@ class ElementListener extends Listener {
           new FieldElementX(name, compilationUnitElement, fields));
     }
     NodeList variables = makeNodeList(count, null, null, ",");
-    TypeAnnotation type = popNode();
+    popNode(); // type
     Modifiers modifiers = popNode();
     buildFieldElements(modifiers, variables, compilationUnitElement,
                        buildFieldElement,
@@ -1553,10 +1552,10 @@ class NodeListener extends ElementListener {
   }
 
   void endTopLevelMethod(Token beginToken, Token getOrSet, Token endToken) {
-    Statement body = popNode();
-    NodeList formalParameters = popNode();
+    popNode(); // body
+    popNode(); // formalParameters
     Identifier name = popNode();
-    TypeAnnotation type = popNode();
+    popNode(); // type
     Modifiers modifiers = popNode();
     PartialFunctionElement element = new PartialFunctionElement(
         name.source, beginToken, getOrSet, endToken,