Start making server strong mode clean

pkg/analysis_server/lib/src/search/element_references.dart

Index: pkg/analysis_server/lib/src/search/element_references.dart
diff --git a/pkg/analysis_server/lib/src/search/element_references.dart b/pkg/analysis_server/lib/src/search/element_references.dart
index 0608764419ffbdbde1663dee9ff048d7fa9b4c9e..74c72ef4ba2a86d1e96ecb29ff3842ed2bab81b3 100644
--- a/pkg/analysis_server/lib/src/search/element_references.dart
+++ b/pkg/analysis_server/lib/src/search/element_references.dart
@@ -46,20 +46,19 @@ class ElementReferencesComputer {
    * Returns a [Future] completing with a [List] of references to [element] or
    * to the corresponding hierarchy [Element]s.
    */
-  Future<List<SearchResult>> _findElementsReferences(Element element) {
-    return _getRefElements(element).then((Iterable<Element> refElements) {
-      var futureGroup = new _ConcatFutureGroup<SearchResult>();
-      for (Element refElement in refElements) {
-        // add declaration
-        if (_isDeclarationInteresting(refElement)) {
-          SearchResult searchResult = _newDeclarationResult(refElement);
-          futureGroup.add(searchResult);
-        }
-        // do search
-        futureGroup.add(_findSingleElementReferences(refElement));
+  Future<List<SearchResult>> _findElementsReferences(Element element) async {
+    Iterable<Element> refElements = await _getRefElements(element);
+    var futureGroup = new _ConcatFutureGroup<SearchResult>();
+    for (Element refElement in refElements) {
+      // add declaration
+      if (_isDeclarationInteresting(refElement)) {
+        SearchResult searchResult = _newDeclarationResult(refElement);
+        futureGroup.add(searchResult);
       }
-      return futureGroup.future;
-    });
+      // do search
+      futureGroup.add(_findSingleElementReferences(refElement));
+    }
+    return futureGroup.future;
   }
 
   /**
@@ -149,9 +148,9 @@ class _ConcatFutureGroup<E> {
    */
   void add(value) {
     if (value is Future) {
-      _futures.add(value);
+      _futures.add(value as Future<List<E>>);
     } else {
-      _futures.add(new Future.value(<E>[value]));
+      _futures.add(new Future.value(<E>[value as E]));
     }
   }
 }