Use entities in impact transformers.

pkg/compiler/lib/src/universe/resolution_world_builder.dart

Index: pkg/compiler/lib/src/universe/resolution_world_builder.dart
diff --git a/pkg/compiler/lib/src/universe/resolution_world_builder.dart b/pkg/compiler/lib/src/universe/resolution_world_builder.dart
index cd2593ed383f7d8bd73dd1d639fa60d515e54818..ff1057bc522af1974fabe17ec02f9f2621c907d6 100644
--- a/pkg/compiler/lib/src/universe/resolution_world_builder.dart
+++ b/pkg/compiler/lib/src/universe/resolution_world_builder.dart
@@ -565,6 +565,17 @@ abstract class ResolutionWorldBuilderBase
   }
 
   void registerStaticUse(StaticUse staticUse, MemberUsedCallback memberUsed) {
+    if (staticUse.kind == StaticUseKind.CLOSURE) {
+      Local localFunction = staticUse.element;
+      FunctionType type =
+          _elementEnvironment.getLocalFunctionType(localFunction);
+      if (type.containsTypeVariables) {
+        localFunctionsWithFreeTypeVariables.add(localFunction);
+      }
+      localFunctions.add(staticUse.element);
+      return;
+    }
+
     MemberEntity element = staticUse.element;
     _StaticMemberUsage usage = _staticMemberUsage.putIfAbsent(element, () {
       if ((element.isStatic || element.isTopLevel) && element.isFunction) {
@@ -589,8 +600,8 @@ abstract class ResolutionWorldBuilderBase
         fieldSetters.add(staticUse.element);
         break;
       case StaticUseKind.CLOSURE:
-        throw new UnimplementedError(
-            "registerStaticUse not implemented for StaticUseKind.CLOSURE.");
+        // Already handled above.
+        break;
       case StaticUseKind.SUPER_TEAR_OFF:
         useSet.addAll(usage.tearOff());
         methodsNeedingSuperGetter.add(staticUse.element);