Re-land "Add support for metadata on type variables to Fasta parser." (with fixes).

pkg/compiler/lib/src/parser/element_listener.dart

Index: pkg/compiler/lib/src/parser/element_listener.dart
diff --git a/pkg/compiler/lib/src/parser/element_listener.dart b/pkg/compiler/lib/src/parser/element_listener.dart
index be504f68da6e122903ec4fa7309d2ce4a9141a7b..faad8521598996f7c319ffd0176355bac684994c 100644
--- a/pkg/compiler/lib/src/parser/element_listener.dart
+++ b/pkg/compiler/lib/src/parser/element_listener.dart
@@ -76,6 +76,9 @@ class ElementListener extends Listener {
   LinkBuilder<MetadataAnnotation> metadata =
       new LinkBuilder<MetadataAnnotation>();
 
+  /// Indicates whether the parser is currently accepting a type variable.
+  bool inTypeVariable = false;
+
   /// Records a stack of booleans for each member parsed (a stack is used to
   /// support nested members which isn't currently possible, but it also serves
   /// as a simple way to tell we're currently parsing a member). In this case,
@@ -250,8 +253,13 @@ class ElementListener extends Listener {
     if (periodBeforeName != null) {
       popNode(); // Discard name.
     }
-    popNode(); // Discard node (Send or Identifier).
-    pushMetadata(new PartialMetadataAnnotation(beginToken, endToken));
+    popNode(); // Discard type parameters
+    popNode(); // Discard identifier
+    // TODO(paulberry,ahe): type variable metadata should not be ignored.  See
+    // dartbug.com/5841.
+    if (!inTypeVariable) {
+      pushMetadata(new PartialMetadataAnnotation(beginToken, endToken));
+    }
   }
 
   @override
@@ -419,7 +427,13 @@ class ElementListener extends Listener {
   }
 
   @override
+  void beginTypeVariable(Token token) {
+    inTypeVariable = true;
+  }
+
+  @override
   void endTypeVariable(Token token, Token extendsOrSuper) {
+    inTypeVariable = false;
     NominalTypeAnnotation bound = popNode();
     Identifier name = popNode();
     pushNode(new TypeVariable(name, extendsOrSuper, bound));